PS2 is more profitable to develop for? If you develop a PS2 title chances are you can port it to the PSP, PC & Wii.
Exactly as as hadrian said... its very easy to port between the ps2 and wii, so i think that as long as wii is around probably ps2 will to, cause they will probably make very very cheap ports from wii games to ps2. and get easy and fast cash... and if you look at every past generation, "last gen" consoles has always been supported a few years into the "current gen" systems lifespan.. the NES had allot of titles released even after the Genesis/MD and SNES was released.

