I agree, but not like they are going to fire him on the middle of the season, they are going to look for another driver after the season is over. We still have plenty of races left, and could Perez make a comeback and keep his position? Maybe, if he ends up being the second (or even a few times first) this season and keeps that up for all the races that is left, I think he could still convince the team to keep him. However, we have seen him not do all that well so far, and I do not see a reason why he would get any better suddenly. The real question would be who to get instead of him, Daniel Ricciardo is a great driver but feels like he is way too old to become a second driver to them, I think a young talent, someone 24 or younger should be the point, that would allow them to get a talent that could give them at least a decade with them and would make more sense however there aren't that many of those available right now.
Perez can make a comeback on his performance or not at all(?), no one knows, but what is certain is that his seat is wanted by other drivers and the possibility that he will be replaced by RBR is very big if you see how RBR is quite firm in firing drivers even in the middle of the season. It's even possible that Perez could be in 3rd place if Hamilton can get a good place in the remaining races ahead and if that happens it might be a strong case for RBR to replace him.