I just can't think who they could replace Kimi with that is better. I can't see top line drivers like Hamilton or Vettel really go to an under performing Ferrari within the next year or two, given the performance? Likewise would someone like Hulkenberg want to switch given the current dominance of the Merc engine. Maybe Button will be a free agent next season but is he really any better than Kimi.
I think Ferrari are probably 'stuck' with Kimi for the next 2 to 3 years, in the same way Alonso is stuck with Ferrari at the moment. These rumours may be just coming from the press or they may be from someone in Ferrari who is trying to stick a rocket up Kimi's bum?
Either way I think Ferrari need to suck it up and develop a better car/engine combo for next year, and Kimi needs to find a way to better deal with the dog turd he is driving this year.