My instincts tell me that it'll take more than John's retcon-powers. Doomed timelines follow the rule that "anything that happens, stays happened", inasmuch as a doomed timeline happens when something/someone/some information travels back in time to the Alpha Timeline from within the doomed timeline and changes things, whereas John makes things un-happen without any information coming from the alternate timeline (c.f. the argument between Dave and Grimbark Jade), and I think we've spent a little too long in the current doomed timeline, and too many things of consequence have happened, to just "erase" it like that.