I'm hopeful they won't be stupid enough to try impeachment again. Impeachment is like a referendum: you should only go for it if you know you're going to win. Wilson knew he'd win the referendum in the seventies before he called it; Cameron assumed he'd win and we live with the consequences.
There is zero prospect of successfully impeaching Trump, so go for the acolytes as others have said. I don't think Americans voted for two years of navel-gazing from the Democrats. It seems that corruption was a big issue in the elections, so spend the two years exposing as much as possible and tarnishing the Republicans. I don't think Vance is a realistic Presidential candidate; he's too tainted. Rubio or Cruz will have a punt, along with some other soulless religious freaks. I'm sure Vance will give it a go, but Trump succeeded purely on strength of personality and his ability to lie and bullshit with zero consequences. Hopefully he's irreplaceable and the Republicans will spend some time in the wilderness.
Never underestimate the ability of the Democrats to self destruct though. Who are their possible candidates? Newsome will give it a go, and I'm sure the "progressive" wing of the party will have their favoured candidates.