I think it's more likely PC gaming gets marginalized further like has been the case for many years already. The PS3 is already technically capable to take gaming beyond top PC showcase titles such Crysis in significant ways. The best sold PC games aren't especially demanding.
I think in the future less people will upgrade or buy new PCs, consumers are already wary of Vista. For gaming and movies, entertainment in general an advanced dedicated low effort device like the PS3 IMO makes more sense underneath HDTVs for many consumers.