Metacritic alone won't determine what happens to them. Killzone scored "low" and Sony bought Guerrilla Games after. Evolution Studios was never known as one of Sony's top-tier developers. They basically make the racing games for Sony platforms that Polyphony Digital can't be bothered with which is still an important market for Sony to have its own developer for, especially with Sony Liverpool closed a couple years ago.
We also have to consider that this problem may indeed have been the result of the previous director. Pete Dodd may have actually been correct with his assessment and the guy wanted to save face so he made his own counter claim that everyone accepted as truth. My guess is that this game was a disaster behind the scenes and it was everything the new director could do to make it passable.
This isn't the same scenario as Santa Monica's game that Asmussen was in charge of that was in development for 4 years and they literally gave up on it ever being even just good enough. That large layoff was justified even if it still sucks that it happened. The more likely scenario is that a few people will be fired, the studio will be given a new direction, and Sony will see how sales turn out after the holidays before they make big moves, assuming they find it necessary to begin with. There is no reason for Sony to close them right now. Their games division is not hurting at all. Now, if we get closer to the end of the generation and Evolution Studios has dropped the ball a few more times then Sony may decide to cut "proven dead weight".