Don't think you can have a 38-match season *and* have playoffs. One or the other. Unless you want to sit in Yankee Stadium in February for the season opener, that is.
I guess you'd probably need more midweek games to make it work. But if you care at all about a balanced schedule, the expansion will require a longer regular-season.
I would be in favor of shortening the playoffs. 16 teams, knockouts only. Higher seed gets the home game. My main issue with the current playoff system is that there isn't enough of an advantage to the higher-seeded team. Making it a knockout bracket with higher seeds hosting would solve that issue.