Like the OP's other thread, I also adore this game. There was just something that made it click for me, even if I only bought it initially for Uncharted 2 beta access. The problem is, it just never gained great traction sales wise, so it isn't as important as Sony's other franchises
Out of those franchises, I think only Killzone should really continue. Resistance was never a big seller after the first one and I personally never bothered to play the 2nd (it is sitting over to my left barely touched) though I am certainly tempted after the good reception of the 3rd. I said many times on this forum that I feel Kratos has had his time, but he does sell....
Anyway, I feel Sony did a great job introducing new and interesting franchises from their 1st and 3rd party studios (though of course, now Sucker Punch is 1st party and Insomniac not even 3rd party) and I hope they do the same again this gen. It is rare that series actually justify more than about 3 games, there are only so many things you can do apart from just changing characters. It is probably good for the studios to have a bit of change as well
Of course, new IPs are far more risky than sequels, but Sony has generally kept a good balance