As a confirmation, we're working really hard to make sure as much of the data is carried over. The only thing we can't carry over is passwords, so when you first log on to the new forum, you'll need to set a new password.
This will probably be done over email so make sure the email you have registered with THIS forum is your email and not ... say a burner email account like mailinator or something like that.
I don't think email is a good way for users to create new passwords for their account. I am fairly sure that there are no small number of users who have used a fake/invalid email address to be associated with their account.
It should be trivial for most people to simply change their email address associated with their account however there are probably a good number of people who will not be active around the time the new forum goes live which means they could permanently be locked out of their account.
I'm not sure what to say. If you don't have a valid email, there's no way to securing send you the link to register your password with the new forum. If you have a better idea, I'm more than happy to listen. If a user hasn't been using their account on the forum for a long time... well chances are they haven't been using the site much either. Either way, they can always just make a new account.