Pretty sure they've already hinted in an onterview that NG+ is going to just be "pick a solo instance from a list to replay it", not redo all quests from the beginning. It would make sense: no one's starting over just for the dialog and fetch quests, and they'd have to take lvl sync off from those solo instances anyway, so might as well make special queuable solo instances where you have your current level and gear.

Not sure why people are betting so much on it when we barely know anything about it.