PA(OPEN Toomey-R) is the only US Senate seat up for re-election in 2022 that will definitely flip.

PA is an open seat in a weak blue(Biden-D) state and plenty of top tier Democratic candidates.
Wolf-D(term limited from seeking another term for Governor)
Fetterman-D(current Lt. Governor likely to run either for the US Senate or Governor)
Shapiro-D(current Attorney General likely to run either for the US Senate or Governor)
Boyle-D(US Representative from PA-2cd)
Houlahan-D(US Representative from PA-6cd)
Lamb-D(US Representative from from PA-17cd)
Democrats will pick up WI(Johnson-R) and NC(OPEN Burr-R) if 2022 is a Democratic wave election year.
Democratic candidates in WI(Johnson-R)
Barnes-D(current Lt. Governor)
Kaul-D(current Attorney General)
Godlewski-D(current Treasurer)
Pocan-D(US Representative from WI-2)
Democratic candidates in NC(OPEN Burr-R)
Jackson-D(current state senator)
Smith-D(former state senator and 2020 Democratic US Senate candidate)
Governor Cooper-D is unlikely to run for the US Senate in 2022 because the current Lt. Governor is a Republican but is likely to run for the US Senate in 2026 against Tillis-R.
Democrats will hold onto
GA(Warnock-D)
AZ(Kelly-D vs Ducey-R)
NV(Cortez Masto-D vs Sandoval-R)
NH(Hassan-D vs Sununu-R)