Trust me, I'm The Doctor.
The NFL’s official position is that it’s planning to play a full season in full stadiums. It’s unofficial position is far more pragmatic. According to the Washington Post, the NFL’s contingency plans include a shortened schedule and playing games in empty or partially empty stadiums. “As we have...
I've seen it mentioned elsewhere that you can have 4000 people fill a 60,000 seat stadium and still easily meet social distancing guidelines. I think that a plan starting with games in empty stadiums or fields, then small crowds, eventually working back up to full crowds is the way to go.
There are other factors to consider like when will a vaccine be ready? We may not be able to allow 50,000+ people in a stadium until we're sure that we've achieved some level of herd immunity from covid-19.