Pokemon generally doesn't get announced at E3 - it's one of those franchises that almost always gets announced in Japan first.
If a new Pokemon game of any sort gets announced at E3, it'll be a spinoff that is designed more for the west. One interesting possibility is Pokemon Snap 2, because Pokemon Snap sold far better in the West than in Japan (over 2 million in North America, another 700,000 in PAL regions, and about 650,000 in Japan), at least according to VGChartz.
A Wii U Pokemon title might also end up being announced at E3, as both Colosseum and XD sold better in America than Japan by a noticeable amount... but I doubt it, because Nintendo would probably want to use it to push the Wii U in Japan most of all. This observation also applies to the slim chance of an MMORPG - if it's happening, it'll probably be announced in Japan.
Personally, I'm not expecting any new Pokemon announcements, just further information on the new Super Mystery Dungeon and possibly the first information on Pokken Tournament outside of Japan. This isn't to say that I don't seriously hope for Pokemon Snap 2... but I don't expect it.







