Or save blobs + APticket from 5.0 before upgrading, using iFaith, just so you don't miss the upgrade window when 5.1 is released. That may happen before the JB is released, in particular if they hope (but they cannot know!) that it will still work on 5.1, and in particular if they hope to get it working on a 4S and don't want to burn that chance.
I'll save blobs with iFaith and then upgrade.
(iFaith is Win only, so it is a bother for us Mac users. We need to borrow a laptop/PC with iTunes installed, run iFaith and hope it works. I had to try two laptops before it would work, iFaith seems to have trouble recognizing that the phone is in DFU mode even if redsn0w or iTunes sees it just fine).