Well yeah, the DS was and is huge.
Not sure how a new Mario game and a new Mario Kart game qualify as "not supporting the system" (with another Mario, a Smash Bros., a Fire Emblem, and a Zelda coming down the pipeline, though some of these are just announcements and could conceivably of course be cancelled). Again, there's no precedent for having Pokemon jump to a new system mid-generation (Yellow was indeed classic GB), so I wouldn't read too much into Black/White 2 being for the DS.
I'd put good money on the eventual gen 6 being on the 3DS.