Will college football return in 2021?

Yes.  Expect at least one of the many vaccines in the works to have passed muster and be widely distributed by then.  Corona may never 'go away', but our treatments and testing and vaccines will make it a MUCH smaller deal by next year.

Not in my opinion. I think it is done for good.  With this new disease we have (COVID-19), I don't think sports will ever be safe to be played again. A vaccine is just not going to happen or if it does it will be like 30 years from now. We are still looking for that HIV-AIDS vaccine promised by 1990. 

It will if the pandemic situation is a lot better. It won't if there isn't much change from today.

It is possible that it could return.

Since none of can see into the future, the best answer I can give is: I don't know.  We can make predictions about the return of college football based on what's happening, but it's really just an educated guess.  

Listening to ESPN radio it's amazing that their talking heads continually slam the amateur player  college divisions that decided to pull the plug on the season because of a world pandemic but at the same time advocate shutting down the professional NBA  for BLM  protests.

If Trump is re-elected, you can pretty much kiss many sports goodbye because players will be infected again and again and they will be dropping like flies. The virus is not going away simply because Trump thinks that it will. It will only go away with proper pandemic control measures like isolation of the infected, extensive testing, and preventive measures like social distancing and wearing face masks.