The issue all these sports are now facing is very similar to what you saw with television over the last 35 years. As cable and satellite TV made it easier to get more and more options on the screen, it diluted the viewership to the point where nobody gets substantial ratings anymore except for occasional spectacles like a Super Bowl or a presidential debate.
Perfect case in point: Los Angeles. It's one of the largest metro areas in the country, and yet sports teams often struggle there because -- well, because there are so many sports teams and entertainment options for people there.
last year I read that MLB was picking up many viewers and fans that pro football lost.
What you point out is a very good possibility.
Which is why baseball stadiums are getting smaller and the crowds still cannot fill them up. Even NBA games are full of empty seats. Too many games in the season waters the sport down.