There will not be another Animal Crossing for the 3DS (it's been one per handheld/console) and the next Pokemon game will come out after you become a co-assistant. Since you have time before then, might as well play them while you can. Both games will deliver many hours of gameplay.
Is there a reason why you want to sell your 3DS? Keeping it may be useful if you plan on buying another game in the future.
It seems that I'm just going to purchase one, but maybe 2 more months. Thinking of playing the 3DS XL whenever I get bored. Thanks everyone. Can't wait to become a Pokemon Trainer and citizen in Animal Crossing :D