In 2022, there are 34 Senate seats up for election. 20 are now red, 14 (counting Warnock) are now blue.
Two incumbents up for re-election in 2022 have announced that they won't be running again. Both are Republicans in blue/purple states. Toomey in PA and Burr in NC. On top of that, Johnson, R from WI, would seem to be vulnerable, as he is a rabid Trumper in a state that went for Biden. Also, Grassley, R from Iowa, is going to be something like 89, so we'll see if he runs again. If not, Iowa would be another potential pickup for the Democrats. So the Dems have a pretty good chance to pick up these 3-4 seats at least.
On the blue side, Warnock will be seen as vulnerable. Plus, there are Dem incumbents in purplish states that maybe aren't a lock for re-election (CO, NV, NH), although I have no idea how popular these Senators are at home.
All in all, it looks like a somewhat favorable electoral map for the Democrats in the Senate in 2022.