They have 54 dems for sure, maybe 56 if remaining undecided seats go dem – since those two remaining seats are currently leaning dem, let’s assume they’ll have 56.

A 2/3 supermajority requires 67. They’ll need 11 of the 44 Republicans to go along with it. Yes, that’s kind of a big ask, but it’s only 1/4 of them. And in the Senate in particular, some of them will be looking at trying to get reelected in 2028. A presidential election year, which already doesn’t usually bode well for Republicans. After looking at what happened in the midterms, I think it’s plausible that you could find 11 Republicans who are willing to throw Trump under the impeachment bus in order to distance themselves from him and improve their reelection chances.