The problem with this is, some clever team already decided that 5 starters, instead of 4, works better...and everyone followed suit. And before that, some clever team decided that three starters was too few...and everyone followed suit. And before that, some clever team decided that one pitcher per game, who pitches the entire game come hell or high water, wasn't the best way to play the game...and everyone followed suit. Pitching has been evolving since the second year of organized baseball. Just because everyone did it that way a couple years ago has never prevented experimentation. Not today, and not 100 years ago. Pitchers pitch fewer innings. That's been a trend forever, and I dont see that changing. I think it's more likely we see roster expansion than a return to smaller staffs with 5 Traditional starters.