I kind of doubt they'd do it. The soccer was different, reducing the tournament draw (plus MLS currently intends to have a season, including making up three missed tournament games that count in the league standings). MLB or the other 28 teams would also have to pay the salaries of the cancelled teams.
I'm not even suggesting the Phillies and Marlins are the teams it will happen to. They've got time to resume the season, even if obviously truncated. But what if it happens again in three weeks? Five to six weeks and I suppose you do probably just end a few teams' seasons and continue. But what if one of those teams was the Dodgers or Yankees?
Plus the season is so freakin' short. What if our 1-2 Phillies are, say, 10-16 on August 25th? Will players opt-out? Harper's been pretty cavalier about everything, but his wife is still pregnant. And would Didi or Arrieta or JT get traded?