Well I do think it may be raised more then 2 or 3 lvls but I also think some higher end content will be released to go along with it... IE tougher quests and mobs, maybe even a new area instead of another instance.
Instance dungons are like these caves that when you go in it kinda seals you and whoever went in with you into a different dimension.... IE once your so far in no one else can join you in that cave, however if someone else goes into that cave with another group they will be spawn into the own individiual copy of that cave.
