I could see summons being used as a one time attack, kind of like your 2hr ability in FFXI. You pick a summon (you can change summons every now and then if they granted your their strength) and use it in combat in those tough situations where it can save the day.
I would very much like to see SMN come back because it's a very important aspect of every Final Fantasy game (imo) but as it has been said, it's hard to picture players walking around with Ifrit or Garuda this time around (the main storyline explains why I'm saying this).
I never played SMN much in XI but it was a vital part of the game.

PS: SMN wasn't broken, what happened is you probably saw terrible summoners... which isn't surprising considering half of them didn't have a clue.