Let's do a thought experiment. Donald Trump has been a businessman for a long time, and it seems pretty clear that he has engaged in transactions that he doesn't want to be made public (otherwise he would have released his taxes). I read the Manafort indictment, and Paul Manafort engaged in a sophisticated money laundering scheme for many years without being caught until someone took a close look at his finances.
I don't know for certain Trump has committed a crime, but let's assume that an actual crime is hidden in his finances. How will he respond if he thinks Mueller is close to uncovering it? Trump already declared that his business dealings were off limits, and Mueller clearly isn't going to respect that declaration. So what might Trump do if he is desperate to keep Mueller from finding out something that either he or one of his family members has hidden in past business dealings?
I think his first course of action would be for him and his allies to try to discredit the investigation and deflect. Of course, he has been doing that for some time, but it hasn’t stopped Mueller.
But think about it. Mueller is closing in on Trump and his family. Trump knows it. He is trapped. Given his prior actions, what will he do? I think he is absolutely going to fire Mueller. It will precipitate serious fallout, but if he is trapped he will take his chances and assume dealing with the fallout is better than being charged with a crime.
I really can’t see any other outcome. Trump isn’t going to just sit there and let Mueller close in and indict everyone. That’s not his style. He will move on Mueller. I think they already have enough to indict Trump Jr., so at some point soon Trump’s hand will be forced.