people are making the assumption that resolutions are simply going to continue to get smaller and better, but the fact is that there are very real physical limitations with cellphones regarding screen size, and even when clean 3d resolutions become accessable i tihnk much of what goes on will favor pixel art for its clarity. i could be wrong but i doubt it.
Mobile is already moving in the 3d direction. Look at a few of these titles available on the V-Cast phones:
Madden NFL 07 (coming soon, the trailer looks tasty)
Need for Speed Most Wanted
Massive Snowboarding
The bigger players in the wireless gaming industry seem to be looking more and more for low-poly 3d artists. However, a good chunk of 2d work is needed by the small independent developers.
Pixel remains viable for GBA and DS also, but I feel that most reviewers tend to be less impressed by it, seeing it as a sort of nostalgic appeal to the games of yesteryear.