The HD Twins strategy and longevity will be decided by who blinks first.
If MS produce a sucessor to the Xbox 360 next year expect SONY to redouble their efforts and rush PS4 to market.
SONY will not be happy playing catch up to Microsoft again.
I know that a lot of people say the PS3 is future proof but in a sales battle that is meaningless.
All the people on the street will know is that the PS3 is a last gen machine and therefore "OLD TECH".
Nothing sells to the masses like "new and shiny"