I have been waiting for 0S4 for my 3GS but my 3GS is Jailbroken with 3.1.2. (blackrain) :confused and I enjoy the benefits with the JB. Should I upgrade or wait?
If you're gonna miss the jailbreak that much then just stick with it.
Personally I've always jailbroken but I don't see any reason why I
will anymore. I like iOS 4 stock the way it is.