There is no way in hell apple will put 512GB SSD on MBP without charging an arm for it. So, don't dream..
What if apple makes the MBPs premium priced machines again, like, starting at 1399 for the base 13" model? The 800-1200 range is getting so crowded (MBAs, ipad 2, MB). Can't say apple would leave high school kids, cheap college students and email-checking-granmas without options.
The repositioning of MBPs would allow for standard 300-512gb SSDs. Also don't forget that SSDs prices will suddenly drop in 2011 tnx to 22nm flash chips. Kinda the summer 2009 drop tnx to 34nm chips. We're talking double the capacity for the same price tag.
I want to believe.
(in SSD-only 2011 MBPs)
Anyway i'd be just as happy with an iMac27-like hybrid ssd+hdd solution. I would call it unnecessarily complicated (for an apple laptop) but since it's already happening on imacs, it could happen on MBPs.