The reason I've felt that Manafort has held out from flipping thus far -- with two trials ahead and mounds of supporting material in his various indictments and his former partner Rick Gates having plead guilty and supplying evidence for the prosecution -- is not because he's expecting a pardon, but...he would rather face life in jail than the Russian mob.
Paul Manafort worked intimately in the Ukraine and with Russian oligarchs. He owes perhaps 10 million dollars to one, Oleg Deripaska. That debt is likely why he offered to run Trump's campaign for free, to get inside so he could pass along information and pay off what he owed.
It's my sense that Manafort is up to his ears with Russian oligarchs, which is the equivalence of being up to his ears to the Russian mob. And if he were to flip for a better deal, Robert Mueller would want something worth that in return, and pretty much all Manafort can offer of that value which would be information on the Russians.
It is probably reasonable to assume that the Russian mob doesn't like that sort of thing. And I'll make another leap -- that Paul Manafort knows this. He may have even been told it directly. And perhaps not only has his life been threatened, but more to the point so too those of his family. And if that's so, he won't flip. He'll go to prison for the rest of his life. It seems to me the only substantive reason why he is the only American under indictment who hasn't yet flipped and with so much from the prosecution pilling up against him.
Mind you, it's possible he simply thinks he can win at both trials and be completely vindicated. But he (or most anyone) doesn't strike me as that much a risk-taker or delusional. It's also possible that he's been promised a pardon by Trump. But I think anyone who's known Trump for as long as Manafort has knows that the one thing you don't rely on is a Trump promise about anything. So, that seems to pretty much leave "I'll take 'Threats from the Russian mob' for $1,000, Alex" as the only reasonable explanation.
Obviously, I could be totally wrong. Or wrong in part, he might flip tomorrow -- though still right about why he hasn't up to now. Of course, even if he does get convicted with a jail sentence of decades, Trump could pardon him, for all we know. So...who knows?
But -- if I was to enter an office pool, my bet would be on "Not flipping" and "Russian mob is the reason."
If I'm right, the good news is that I'd only have to split my winnings with Nicolle Wallace.