Well I guess a zdps monk is the closest thing to support. They just buff and debuff, if they go that route I can't say I'll be impressed. They have a nice bit of DPS and a weird shielding mechanic, but why add another shielding class.
I guess the real healing will most likely be done by a Priest like Velen, or Anduin. Vol'ijn is my off the wall wildcard tho. I can see some sort of other StarCraft support, maybe a medic.