I am going to be more realistic then your average forum poster and look at things from a current perspective. This post is composed of parts of my opinion but I do think its time people started waking up. What is the reasoning behind this prediction? From what I see its composed of the following theories. Theories I will point out where holes exist.
1. It happened with Wii so it will happen here.
Ok now for starters this has absolutely no backing behind it. To say it happened last time so it will happen this time is foolish. Lets look at last generation. Last generation Sony was top dog. Their global domination made people absolutely positive that PS3 would destroy everything. Yeah... about that. Secondly, Microsoft was in a worse position than Nintendo themselves. If you look at this from a business perspective Gamecube was better off. What is more successful? The system which sells 22 million at profits or the system which sells 24 million at a loss for every single one?
It seems people have forgotten exactly how bad Microsoft had it last generation. Personally I believe they had worse third party support then Gamecube. Thats because of the games I'm into. But I'll hit more on this point later.
2. Power was the issue. What happens when PS4 and 720 come out?
This is a good question. People seem to believe that every single 360 owner will migrate to the next Xbox and every PS3 owner will upgrade to PS4. Except that assumption is wrong again. Its proven through statistics that half of 360's user base is composed of people who bought PS2. So no, not every person is driven to follow the system they previously owned. Next they assume things will just carry over. Thats not the way it works. Bethesda have recently gone on record to say they aren't supporting anything until the install base justifies development costs. There is also the possibility that all that power will come at a price.
Having such a price will put the system at a disadvantage. Oh yes they will certainly have impressive looking games but what happens if the systems don't catch on quick enough? PS3, 3DS and currently Vita were (are in the Vita's case) all seeing games cancelled, moved or expanded to other platforms because it isn't worth the cost of development. Its entirely possible this could happen with Wii U but its not like 720 and PS4 are exempt from the rule is it? A lot of developers will just take the "wait and see" approach. People might have trust in Microsoft and Sony but (as Bethesda has proven) they aren't blind to just jump in any hardware they do. They want to see a good enough install base first.
3. Third party games don't sell on Nintendo.
Oh dear. The biggest most silly laughable comment anyone can make. This will be expanding on Microsoft's situation in the market prior to 360 coming out. You see people, despite what is the general belief, Japanese developers tend to sell well enough on Nintendo. Look at any Nintendo console (including Wii) and you'll see the majority of support came from Japan. In fact I even remember an article entitled "stop forgiving Nintendo" in which the user was determined to prove Nintendo's games are the only games to sell on Nintendo, only to note the Resident Evil series, Soul Calibur II, Monkey Ball and even JRPGs were the exceptions of the sales. Notice a pattern here? They are all Japanese games. And this is the major reason why its not going to happen.
Nintendo now control 70% market share in Japan. Japanese developers and publishers have all tended to fair well on Nintendo. This is where the claim falls flat on it's face. Lets use Lightning Returns as an example here. If it gets announced for Wii U (and nothing has been denied yet) who wants to bet on which version outsells which? Personally I would wager the PS3 version sells the best because the 3D games have spent so much time on Sony's platforms that people tend to associate the games with their systems. But I would be dumfounded if a game like that sold more on Xbox.
Now this the BIGGEST problem with your theory. This morning it was announced that lovely Japan would not be seeing a version of Metal Gear Rising on the 360. Lets get this clear. Even if you look at games like Resident Evil, they would sell more on Nintendo then Xbox. Want proof? Why has the series spent so much more time and energy with Nintendo than it has with Microsoft's field? Because Capcom clearly see more benefit sticking on Nintendo systems. In fact the series has recently had two portable versions on 3DS and not one on Vita (even though the series started on Playstation). Its hard to say how Metal Gear would fair because the games have sold a similar amount on both Nintendo and Microsoft. The point is Microsoft struggle in Japan.
I wouldn't like to say how Microsoft's position in Japan will effect them next generation. There are increasingly fewer games getting released on 360 there. But it will definitely have a positive impact on Nintendo. No Japanese developer would willingly abandon Wii U for a system that doesn't even sell well over there. Thats probably partly why they see more sales on Nintendo. Nintendo have three parts of the world whereas Microsoft only have two under their thumb. I would argue that last generation Xbox had worse third party support than GC. Thats because I'm really into Japanese games. Microsoft have sold so poorly in Japan that people hae argued MS shouldn't even bother releasing a system there. But they still do. The reason is that the second they pull Xbox from Japan, they immediately lose support from the likes of Capcom, Konami, Namco etc. And they need franchises like Metal Gear and Resident Evil to give their platform more variety.
I would really like your views on this. Why would Japanese developers and publishers leave Wii U entirely in order to support a platform that doesn't even sell in their turf? Can people give me proper reasons to counter mine other than "it happened this time". Despite what a lot of you claim, it didn't happen with Gamecube. That system had a lot of JRPGs. It generally got most multiplatform releases (the exceptions being Rockstar). I don't count stuff like Jade empire as multiplatform because it was published by Microsoft. It had stuff like Hitman, Timesplitters and Call of Duty.
I believe Wii U will lose some Western support but it won't lose support on the scale it did with Wii. Nintendo are working much closer with third parties than they were before. Iwata said they are ensuring its included in multiplatform development. And they pretty much control Japan. Wii U will miss out on some big releases once the other systems start to get their places on the market, but the others could miss out on big releases in other ways. Supposedly Nintendo is extra keen on small developers putting their games on e-shop (like Toki Tori 2). And they have gone on record to say they want to see more support from I-Phone developers. I haven't played I-Phone games but I must admit I find Toki Tori appealing and I'm sure there may be some decent games on them. If the newly announced Ninja Gaiden plays well (ignoring the cards) and similar to Dragon sword on DS, its got the potential to be an extremely addictive and compelling game. I still think that is one of the best DS games to date and I think better than any game on PSP.
These are the reasons I've seen people commenting frequently. Are there reasons I missed? Do you agree with me? Or can you really see Wii U support being as bad as Wii? I think at worst it would be a Gamecube situation but there is no way I see this being a repeat of the Wii. There are too many things contradicting that this time.