So my girlfriend is pretty indifferent about updating her iPhone, and is still on 4.0 (not jailbroken). Once the new lineup is released, I'll be getting the new one and giving her my iPhone 4. We would like to get the best value for the 3GS, so I was wondering if we could jailbreak and unlock it before selling it. Obviously she has not been saving her SHSH blobs, so would it be impossible to securely wipe the phone without updating the software? If so, she may as well update to 4.3...