Should I expect JB to preform better than ICS?
On lower hardware particularly. I've got a Nexus S and the ICS update for it has been terrible. Memory managment is abysmal and I get force closes on everything. I shouldnt have to worry about my background tasks, but with ICS I have to.
Maybe a solution like MS's where they reduce the system requirements for their OS every time but add new functionality. If they can do it, so can Google.