Not if all Trump supporters joined.
That is my whole point. Who would stay?
If all Trump supporters left to form this new party, and the Republicans that aren’t Trump supporters stayed behind, then you’d be guaranteeing Democrat control forever. It would be just like California. The only way that any conservative policies could be enacted would be if the Trump supporting party and the Republican remainder decided to work together on something, which, coincidentally, is what already happens with both of those groups in the Republican party. If all the Republicans that AREN’T Trump supporters said “ah, screw it - if all those other people are leaving to form this new party, then I’ll join them” then what would be the point? You’d be taking X (Trump supporters) and Y (non-Trump Republicans) and moving them from one party to another.