McConnell is on record as saying that he won't allow a vote on impeachment before he becomes minority leader. Trump is likely to be impeached by the House, since Pelosi has already vowed to bring it up for a vote. It is debatable whether a Senate trial would lead to any consequence after Trump is gone. Impeaching Trump next week would send a strong symbolic message, but that is about all. The precedent now is that chambers of Congress controlled by the president in power shield him or her from danger of impeachment. The guard rails have been removed, opening us up to a greater likelihood of one-party rule in the future.
Apart from the material benefits Trump would receive from completing his term, like pension, Secret Service detail, and travel expenses, an impeachment would put the test to the Republicans to see if they want to own what Trump does through 2024. There's no precedent to set here, as it seems more likely that some attrition affects the Republicans' vote, nor do I see the Democrats using this as a model for behavior in the future.
The Rs would be setting precedent for their future behavior and nothing else. Indeed, it's a call for bipartisan reconciliation after Trump's insurrection. They could excise him from the party and show that they support their country over their party. Having no vote is equivalent to a
No vote; Trump is the albatross around the Rs collective neck and I don't think anyone in either party currently thinks they're interested in anything except partisanship and one-party rule. It would be a literal escape hatch