I'm not sure if Flynn cut a deal or if his doing so would be the beginning of the end, but I certainly hope so! Because if Flynn has the 'smoking gun' and is willing to deliver it with a shiny bow on it, you'll see Manafort et al lining up behind him to squeal to save their own skins. There is no honour among thieves and that's what they all are, after all. They'll be throwing others out of their way to exit Trump's burning building!!
I've said it before and I'm saying it again, Trump will never resign under pressure. They will have to have rock solid evidence of his direct collusion with Russia before he does. He loves power too much and his ego is too large to ever give up the presidency otherwise. It was the same with Nixon. Certainly his advisors were advising him to resign for the good of the country for quite some time before he actually did resign. It wasn't until it was crystal clear even to the village idiot that he would be impeached and most likely end up in prison that he resigned to save his own skin. Trump will be the same. He will have to be facing certain impeachment and a trial before he goes, and even then I'm not so sure. His ego is so large and he's so deluded that I can see him holding on to the door jambs of the WH as they drag him off kicking and screaming.
The only alternate scenario I see to the above is him getting a bug up his arse as he sees his doom on the horizon and him doing everything he can to sabotage the country in petty revenge and then resigning saying "Fuck you all! Get yourselves out of this mess on your own!".