I'm hoping they drop the +1 Ability Increases from the game. You shouldn't be required to increase an ability score or have the rules futz on you. 3-18 is the adult human spectrum and 19+ are for non-humans and the supernatural. Building in mandatory comicbook hero abilities scores into advancement only narrows the game.
For multi-classing I'm guessing they will go to something like Gestalt characters for everyone. Advancement in another class will be very fast and only affect the key scores like Attack Bonuses and Saving Throws when their split level comparatively reaches their first class. This will mean faster advancement for every class beyond the 1st or "primary" class, but that primary class becomes important then. And character don't start out another class as effectively 1st level characters.
As for the MAD problem, I'm hoping they bring back Ability Score Class Requirements. If you can't play a monk without high enough scores, then you can't play a dysfunctional one. But maybe this can include a variant? For those who like playing Fighters with 3 strength or Wizards with 3 intelligence? Or Monks with MAD, bad scores.
