Crowds would take a hit in October for regular season games when it is cold outside. Plus football of course.
I think it is more likely they just play something like a 120-game season. Maybe add a few games to the existing schedule, but at most extend the season a week.
There is also something about having a winter recovery period that is long enough for players to rehab (which of course is an NBA/NHL problem too since extending their season into the summer for a month has no weather related issues like baseball would).
There is just no good solution to this. I think most leagues just shorten their season and add a few extra games on the edges. It will be interesting to see if basketball and hockey go with shorter playoff series. All those 7-game series just take forever on the calendar. Baseball has many fewer off days, so it is hard to compress that calendar as much.