The way it's always been for me is since you are already running the latest firmware it won't upgrade. But since it was loaded with the shift+restore method It wouldn't just load the next one automatically say 4.2.1. So it's really up to you if you want to restore once it comes out or later when the next one is available.
You won't have to restore tho....the easiest way would be to just download the official update when it comes out then shift update like the beta was installed...then you will be up to date...if you don't trust downloading one thing you can do is if you have a second iPad you can update that one then grab the restore image off the hard drive and use that one.