While it’s not inconceivable that you could see an offshoot try to replace the Republicans, I doubt it would happen.

It really depends heavily on timing. If Trumpism fades almost immediately after the election, the GOP can probably survive. If not, there is a good chance of it being replaced. All that would need to happen would be 2 critical steps. (1) A few big conservative big names announce the formation of a traditional conservative party that rejects Trumpism. (2) Over the next couple of years a wave of incumbant GOP senators and congressmen announce they are moving to the new party to break free of MAGA. That new party might still caucus with the GOP but would have a huge amount of leverage over it.