You're looking at the wrong problem, son. This is the map you should be worried about. This is the one the people in Congress and the Senate are looing ap.
Democrats are poised to clean up in 2018 and 2020, which places Democratic governors in state houses across the country. This will allow democrats to, in part, decide the boundaries for 2020 redistricting that first kicks into effect in 2022.
Or let me put this another way: the only win condition in 2018 is these races. If Democrats win the House and somehow win the Senate (where they are likely to lose seats), but lose governors and state legislature races, they still lose. If Republicans hold what they have, and lose at the State level, they still lose.
The winner of the 2018 and 2020 State-level races will be very well positioned to set the tone of the 2020s political climate, much as Republicans did in 2012 and 2014 thanks to their success in 2010 (2010 redistricting first going into effect in 2012).
So no. You're just looking at the wrong problem. If House and Senate Republicans leaders and financial backers see Trump threatening their party's position through the whole of the 2020s, they will throw him overboard with weights attached to his feet.