Republicans would be smart not to jump on the bandwagon. While they may face some hard elections in the short to medium-run, no big tent can be sustained for long. It's impossible to please all the wings of a party, and eventually, they will have to give up certain wings to hold onto others. Then the other party has a way in to break the dominance.
We've seen this happen with Democrats during the breakdown of the New Deal coalition. I see Trump's victory as the complete rejection of that type of Democratic Party. But now Democrats have an 'in' with wealthy, suburbanites and educated whites, who have traditionally been a Republican bloc.
I don't think any of us can say for certain what the coalitions will look like in the future. Its not impossible to imagine a Republican re-emergence in New England, or even states like Washington or Oregon.
If you are interested there are some discussions about this in the rest of the trends board.
There are some difficulties that keep the Republicans locked where they are, particularly religious identity politics, and those states and places you mention are rather secular. Though of course that could change and one thing about Trump was he was able to appeal beyond that barrier to those who were concerned about trade regardless of religious fervor, hence why Maine, NH and such were so close. Though Maine is more religious than the rest of New England IIRC.
