For an impeachment to result in removal from office, you only need 1/3 of the House, but 2/3 of the Senate. Because only about 1/3 of the Senate is up for re-election in any given year, it's pretty much impossible for Democrats to get there in one election. So, even if Democrats take control of the Senate, they would need 15 or so Republicans to go along with it for it to stick. That is extremely unlikely.

Overriding a Presidential veto takes 2/3 of both houses. But I think that is much more likely to happen if Democrats take control of both houses, because they can start negotiating with Republicans and put enough things for them to vote for in bills to reach that threshold. Members will have an easier time voting against the President in individual bills than they would on impeachment. I think he would actually be more pissed off if multiple vetoes get overridden than he would if they successfully impeach him.

what is likely to happen. the opposing (to the white house) party, i.e. the democrats this go-around, gains control over congress. between needing cloture votes for everything in the senate, constant veto threats and the inability to override them, and a lunatic in the white house hell bent on total destruction and swiping everything he can possibly get his or his buddies' hands on.. congress literally cannot do anything to 'fix' anything, due to lack of votes within their own chambers. the corrupt administration continues being corrupt, perhaps even leveling-up their corruption stats even more. congressional democrats start investigations and hearings, but without bipartisan support--nothing could ever come from those. congressional republicants would blame 'nothing being done' by the unproductive session on the majority democrats. come 2028, it's a toss-up again for who and what wins.. it would be a toss-up, anyway, if the elections would be fair.. but they are already not going to be. so we're fucked. we're already raw and bleeding, but they're coming back for more.