Like others have said the laziest devs like Conspiracy would still put out crap.
That said some porting issues would go away like the whole RB debacle with it being such a rushed port that it doesn't work with the GH Wii controller or have online like GH Wii.
But it would be a very stupid decision for Sony to kill the PS2 now. First off the vast majority of the PS2 user base haven't upgraded yet and forcing them to upgrade by killing off the ports and cheap sequels before the PS3 is at a mass market price would be tantamount to sending out ads for the Wii. Also they've cut the costs for the PS3 quite nicely but having the PS2 profit help the bottom line is essential as just a few months ago Kaz wasn't even sure they could be profitable off of the PS3 alone by April '09.
And that's not even considering the fact that Sony probably recognizes the fact that PS2 longevity could hurt the Wii in exclusive software support.
Edit: an interesting point Zen. Many of those titles could be debated though like GH which is even coming out for DS so I doubt it would skip the Wii regardless of a PS2 version to port from.
