The Dems' chances of retaking the Senate are a lot better than they have any right to be. There's a good chance they hold the Republicans to the status quo--which would still be horrific, but better than losing seats.
In 2020, meanwhile, there are quite a few seats that could flip:
Alabama: To R.
Colorado: To D.
Iowa: To D.
Kentucky: To D. (Not because the Democrats should be winning Kentucky, but because Mitch McConnell is ridiculously unpopular.)
Maine: To D. (Probably over anger at Collins' vote for Kavanaugh.)
North Carolina: To D.
Texas: To D. (Yes; it's very possible that it will go Democratic in the Presidential race, which could bring the Senate seat with it.)
West Virginia: To D.
I don't think all of those will flip (in fact, I think the most likely is Alabama), but I'd say that as long as the Democrats can hold the Republicans to no net gain this year (which is very possible) they have a very good chance at retaking the Senate in 2020.