I think you asked this question before, anyways...nobody knows.....
Each jailbreak is different, so the upgrade/jailbraking process may be diference. I've been jailbreaking since day one, and pretty much each jailbreak add something to it that is different from the one before.
So until the actual JB is released and instructions are posted, there is not way to know what the update path will be.
all you got to do is to wait and read up, the instructions will be literally ALL over. All you can do now is to make sure all your SHSHs are saved and NEVER...NEVER under any circumstances do an iTunes Upgrade/Update.
Chances are you will lose all your jailbreaking apps and settings and you will have to re-install them, so yes PKGbacup or a paper with a list of stuff you got install is always advisable