3DS and Wii U versions of Smash won't do cross-play due to having different stages.
Finally the Sony clone does something better than the competition. Though I wonder, if stages are different what else could be exclusive between the versions? I'll be buying both either way.
They do talk to each other though, with Sakurai dropping the very criptic hint of being able to transfer something charecter specific to the Wii U version. All we know is it isn't costumes and won't be tedious to get.
Also, Sorry chaz. No Super Smash Bros Kerfufle. Took the names from the same book as Tomb Raider and Twisted Metal.