I doubt there will be a level cap after EA. Honestly, the Underdark will be more appropriately balanced with Level 5 and 6, and with the amount of experience you can get on the surface alone, you should be at least Level 5 if you didn't just go straight to the Underdark.
Besides, you'll have two paths; Underdark or Cursed Land. So there's lots to do after the original area. If you can gain enough XP to hot at least level 5 by either Underdark or Cursed Land, then they'd have to lift the cap.