The NFL owners have said that they are barely okay with the $175 million dollar cap. There has been zero indication that they are really into increasing that. For the Steelers to not need to cut players in 2021, back of the envelope math says you would need 200-205 million cap. Then maybe up from there if you want to keep fancy things like Dupree and Deion Jones.
It is with NOT counting all the guys you listed that the Steelers are STILL 20 some million over the $175 million dollar cap floor for 2021. So those guys don't free up any 2021 money. Here is one of the many Steelers Depot articles laying out the math of it all:
https://steelersdepot.com/2020/07/po...r-on-steelers/
"..the Steelers are essentially $21.5 million over a $175 million cap number in 2021..."
"Even if the 2021 salary cap number were to come in flat [same as this season] at $198.2 million, you can probably already forget about the team being able to re-sign players such as outside linebacker Bud Dupree, wide receiver JuJu Smith-Schuster, running back James Conner, tackle Alejandro Villanueva, guard Matt Feiler, cornerback Mike Hilton and cornerback Cameron Sutton, all of whom are currently scheduled to be unrestricted free agents in March. Even tackle Zach Banner might be too rich for the Steelers blood come next March."
"...the Steelers could sign Roethlisberger to another contract extension next February to help with the salary cap, but even if they do, the max room that could be created is $14.34 million and that’s only via a faux four-year extension with the quarterback not taking any new money...a more realistic extension that would allow for Roethlisberger to play through at least the 2023 season, would likely result in just $8-10 million or so in 2021 salary cap space being created."
Long story short. Working with the $175 million dollar number, the Steelers are looking at a minimum of $11 million to just get cap compliant for 2021 (that counts a Ben R extension). Then for every guy you sign, you have to come up with the cap space elsewhere. It can be done. They always do. But taking on serious salary amounts in 2021 is likely not in the cards. Additionally there is almost zero chance that Bud Dupree is on the 2021 Steelers roster barring serious injury.
As I have posted elsewhere, I suspect that AV, Feiler, Hilton, McDonald, Haden, VW, Dupree, and Conner are NOT on the roster next season.