I don't think this is going to affect Sony as much as they think it will. They're putting all their eggs in one basket, so far it has paid off though.
Halo is the only reason why the Xbox is still around. Halo was originally going to be released for each console, but when Microsoft bought out Bungie, it became an "Xbox exclusive." They had no mascot/flasgship game, so they had to buy one instead of creating their own. Halo is good, but it's not revolutionary, and Sony and Nintendo probably have something up their sleeves as well.
*Dons flame proof suit*