According to the info Palm presented at the recent developer's conference (and recently confirmed with the 1.4.5. release notes that someone leaked to PreCentral), PDK will not only work for Pixi, but the hardware underneath is just as capable as the Pre of running high performance 3D games. There are minor differences in the implementation (due to differences in their GPUs), but nothing that would block a developer from porting to the Pixi.

The only real hurdle is the different screen resolution (the Pixi is 80 pixels shorter), which would require some UI tweaking if a game wasn't designed with different resolutions in mind to begin with.