I'd have to imagine that Sony would be more interested in getting a new IP from the UC3 ND team. They can go back to Uncharted 4 ~24 months after the PS4 launches and pair it with the first price cut.
I'm betting they view Gran Turismo as the backbone early established IP for the PS4 with GG and Sucker Punch! delivering new launch IPs, with Santa Monica and ND doing the same for the first year anniversary holiday season, plus GG's second team putting out Killzone 4 that Holiday.
Then Uncharted 4 at holiday 2015 with a new Media Molecule IP (after they've done Tearaway for Vita this year) and at least one of the SP! or GG launch IPs getting a follow up sequel here as well.
Sony has a well positioned road map with their core teams. This also doesn't include what Evolution will be doing, anything other than GT from Polyphony from SCEJ, and Sony's penchant for grabbing smaller devs to develop exclusive IPs, even pre-existing Sony IPs.