Yes cydia now saves the blobs although they cannot be used on the 4s as of yet so don't upgrade to 5.1 if your jb on 5.0.1 or you'll be stuck on the new 5.1 iOS.
5.1 offers a few improvements with photo editing and a camera access on the lock screen and reported battery fixes which some say has worked and on balance some has not !
It also rolls out japanese languages for siri !
As i want to retain my un tethered jb on my iPhone 4, i'll opt to ignore the update for now.
You don't need to be on the firmware to save blobs. The blobs are generated by your devices ECID automatically for whatever firmware is currently being signed regardless of what firmware you are currently on.