That's where everything I've read has been leading me, but then what's the 8th class? Every choice I can think of has a problem:
i) If it's the sorcerer as a controller, then the PHB has both controllers as arcanists and vice versa, which leads to a complaint that as in 3rd edition wizards and sorcerers are very similar classes.
ii) If it's the sorcerer as something other than a controller, probably a striker, then there's only one controller in the PHB, and given they have 8 classes and four roles I think the designers would try to avoid that.
iii) If it's a non-arcane controller - I'd bet on the druid - then I can see only one arcane class in the PHB. I think WotC would try to avoid this as well. Unless either the ranger or warlord are actually arcane classes.
Some of my assumptions have to be wrong, but I'm not sure which. Either WotC don't mind having only one arcane or controller class, don't mind that all the controller classes are arcane, the ranger or warlord are actually arcane, or at least one of the Paladin, Ranger or Warlord isn't in the PHB.