I think that it's about time they introduced a new type of Pokemon. I know that the last two, Steel and Dark, were really only introduced in Gen 2 to weaken Psychic, but c'mon...that was super-exciting and it's about time for another one. Maybe a Sound/Music type? That seems to be one of the more popular ones in fanon anyway.
Also, if they're basing their regions on the U.S. now, they should totally do the Baltimore/D.C. area next. I'm not biased or anything.
Lastly, I think it would be cool if they let you bail on fighting the Elite Four without fighting all of them; you'd still have to start over from the beginning (because allowing you to rearrange your party, stock up on Hyper Potions, go to the Pokemon Center, etc. inbetween battles would just make it too easy) but at least you wouldn't have to wait to white out after you've realized it was a bad choice.
I think you wanted to post this in the "What do you want for Gen IV" thread. About the new type, it's already impossible. The metagame is just too advanced to modify the type chart, and also, it would be hard to add the new type to old Pokémon. It wouldn't be nice to add many Pokémon of just one type in the next generation either.
I like the Elite Four idea, though.