Won't happen. But Republicans do know it's free political capital to support him. Especially with Trump mired it legal trouble. It's not like NJ is going to elect a Republican anytime soon, and Phil Murphy is never going to appoint a Republican to replace him.
Sinema didn't switch parties. Switching parties would require joining the Republican party for it to matter in the Senate. Sinema switched to independent (no party) and is still caucusing with the Democratic party.