I have predicted no 2020 NFL season for a while. The NBA and MLB will test the waters, but even if sports that have less contact than football can play, it doesn't prove the NFL can.
Honestly I think the NBA and MLB attempts will fail and be canceled before completion. Some players are going to test positive, and they will be held out. So how will you feel if luck craps on your team and 3 starters are held out while playing another team that has no one out? How about if some star players (the ones who may have millions in the bank to skip a season) decide they don't want to risk playing? Oddsmakers are going to hate this, too. Best case,the 2020 season will have a big asterisk next to it forever.
Then suppose some players get sick, or worse, die? Not only are fans going to be ticked (imagine losing a QB or star RB forever to this virus), but it's going to be a huge PR blow. Think about when 1 player like Korey Stringer or Sean Taylor dies - it's a major shadow over a season. Imagine if 10 died from Covid this year.
Another question is whether employers can be sued (successfully) by an employee who returns to work and contracts Covid. It's expected to be raised in court within the next month and people are waiting to see how it shakes out. NFL owners will have to decide if they mind being sued by players (or their survivors).