If Sony invest on the software side of the PS3: The browser, music player, applications (android compatible), etc. they could easily sell the console as the ultimate Blu-ray player for the casual consumer with the ability to play games, watch photos, & stream movies/music. The PS3 as the "ultimate cheap entertainment center" can still be massively appealing while supplies for the 8th generation consoles is lacking.
Or they can make the PS3 open source and watch those sales rise. Still, I don't think Sony has the balls. They are too afraid of success (oops, I mean risk), and so Nintendo will probably come up with a good strategy keep the Wii alive.
In the end, how the PS3 and Wii fair depends on the strategic moves of their parent companies.