I still believe there will come a point where the Republican Party will pivot on a dime about Trump. They need to play this entire thing very carefully if they are going to save face and minimize damage, but until the time is right they are going to put up the front that they are in it for the long haul. Once solid evidence comes to front and is presented to the public, and if the public "Believes it", they will instantly pivot and downplay any support they ever had for Trump. Unless they believe they can pretend everything is fine for 2 to 4 more years, but I doubt they believe its possible.
A key part of this is likely to get Fox News on the side of the Establishment Republicans when it is time to remove Trump, if the network sides with Pro-Trump Republicans the party will be forced to maintain its front and go all in. But I think the network will side with the Establishment, and do its best to paint Trump in bad light when the party as a whole is ready to pivot.
But its hard to really say who holds the cards in this entire situation, and who they stand with. To me, Trump looks to be in an incredibly weak position, but if someone like the Koch Brothers support him, he may have far more power behind him than I am giving him credit for.