Resistance 4, and the developer seems to think that they won't be working on a fourth game in the series, much like they no longer work on Spyro titles.
In an interview with Gaming Union, creative director Marcus Smith stated, "We've done Resistance 3 and we're really into it and proud of it, but we're not currently slated to do a Resistance 4. So it would be hard to say it's any kind of lynchpin within Insomniac. I think we're thriving and branching out in a lot of different directions."
When asked by Gaming Union if they could see the same thing that happened to Spyro happening to Resistance , Smith stated explicitly that he could see it happening, saying, "Nihilistic is already doing a (Resistance) Vita game, which is going to be awesome. We really respect those guys as game developers. Sony Bend did Resistance Retribution on PSP. We've got a lot of different places for the universe to go, so I could certainly see the series going to another developer. I'm sure Sony would want to find a high caliber developer to do a good offering. I don't think they'd hand the franchise over to somebody who is going to screw it up."
Even flapship titles like Halo now have a different developer, although much of 343 Industries are ex-Bungie devs.