Manchin can do whatever he wants now as far as I'm concerned, except run for President
We've gotten as much from him as is possible for a Senator from West Virginia. His vote was crucial to making Schumer Majority Leader in the last session of Congress, and he enabled SOME of Biden's agenda to pass, giving his presidency some noteworthy and important accomplishments.
Essentially I think of him as a centrist Independent from a State that otherwise elects right wing Republicans. He can call himself a Democrat now or not, I don't care. There used to be other Democrats like him in the Senate. If he chooses to say that the Party left him, I don't give a damn. I'll take his vote when we can get it, I don't look to Manchin for loyalty to Democrats. Unlike in Arizona, there is no potential upside in any other Democrat running against him in West Virginia.
Manchin just needs to stay the hell away from running against Biden in either a primary, or the General Election as an Independent., If so I won't give that much more thought to him than I do to Lisa Murkowski.