If a tease in Dengeki Nintendo DS is anything to go on, we'll be hearing about another Pokemon title soon. Reportedly, "new title information" will be present in the next issue of the magazine, which hits May 21.
That is, unfortunately, the beginning and end of what we know. A lot of fans are calling for a 3DS-bound "Pokemon Gray," but it still seems too early; although, Black and White have been out in Japan for quite some time now. My money's on another spin-off game.
A new Pokemon Snap would be legendary, given the 3DS' depth and augmented-reality capabilities. Not that I think it'll happen. A man can dream, though.
Dengeki Hints at New Pokemon Announcement [andriasang]