Dave, you probably saw already, but there is some discussion of that question on this pinned thread:
Looking To The Future Of Mythical Journeys
I don't know if that helps you or not, but that's the most discussion I've happened to notice.
From a response of JD's on that thread:
> Does our UP roll over into MJ3? I don't know if I
> should be frantically spending it or saving it.
I would continue saving and spending it as normal.
Whether we make any changes to how CP and UP work is a rules question and as such we haven't even started discussing it. But in general, UP is how we thank people for helping us out, and we will want people's help, so we will still need some way to thank you. We did retain UP when we went from MJ I to II.
There will certainly be some kind of limits on the point value of new character when the new campaign starts (perhaps similar to our current spending caps). Starting everyone around the same level is one of the benefits of a new campaign.
I expect that when we get to the one-year mark, we will have more information to share about this and other points. So you will have some advance notice.