Unfortunately, you are correct. The blobs you have saved are specific to your current iPad. When you get a new one, you'd have to save blobs for it - and you can only save what Apple is currently signing (iOS 4.3.5 ... maybe 4.3.4).
However, you may get "lucky" in that the new one may still be running iOS version 4.3.3 (as in, I don't see stores shipping back all the iPads just for a relatively minor upgrade). If you got one still running 4.3.3, you could jail break it, but then you'd have to be r-e-a-l careful with it, because you can't save the blobs and anything you do that'd cause it to need a restore will result in the JB being lost.
Still, could be worth a shot - but, that's not a guarantee...
So, you'll have to pick your poison: Light bleeding on a jail broke iPad or no light bleed on a stock one, with a hope that maybe it's on 4.3.3 (and a vigil started to hope that "they" can jail break iOS 5 soon...).
Sorry 'bout that. Good luck with your decision.
Marilyn