How many US Senate seats will the Democrats will have a net gain of in 2020?

If Biden is the 2020 Democratic Presidential Nominee, Democrats will lose AL(Jones-D). Democrats will pick up AZ special (McSally-R vs Kelly-D), CO(Gardner-R vs Hickenlooper-D), and NC(Tillis-R vs Cunningham-D) McSally(R-AZ) has been appointed to her Senate seat and previously lost the US Senate Election for the other AZ US Senate seat. Gardner(R-CO) and Tillis(R-NC) were narrowly elected in the 2014 Republican wave. +2D.
If Warren is the 2020 Democratic Presidential Nominee, Democrats will lose AL(Jones-D) and if Warren gets elected, MA(Warren-D) until the winner of the 2021 special election is decided. MA Governor Baker can appoint himself or appoint Weld to that seat. The other top tier Republicans in MA are former LT Governors Jane Swift, Kerry Healey, and current Lt Governor Karyn Polito. -2D
Democrats will pick up AZ special, CO, and NC. +3D/ +1D.
If Democrats want to regain control of the US Senate in 2020, Democrats need to pick up two more Republican held US Senate seats. Both GA US Senate seats, ME and either one of the GA US Senate seats, IA and either one of the GA US Senate seats, or ME and IA.