Atrios made a useful observation yesterday. Tax reform is the last big ticket on the Republican agenda and, to them, it is far and away the most important. Protecting and exacerbating the concentration of wealth is their bedrock cause. Once they get their big tax cut, the whole Trump adventure will have been worth it for them.
More to the point, it will also be over. With nothing left to play for, it's probable that we'll see a lot of Republicans quickly lose interest in protecting Trump as his legal problems worsen. They won't need him for anything important anymore so why bother.
Another possibility is the tax cut goes down in flames like the Obamacare repeal before it. That's less likely since the Congress is taking it more seriously this time around. But it could happen. In which case, it will be on to the midterms with no big legislative win to brag on. Either way, the Trump Presidency.. or at least the worst days of it.. might be just about over.