Anyways the update.
John warped back through time, causing the timeline to change, without effectively dooming it (so far)? He intervened on Jade, meaning she never got the chance to kick the Mayor, which results in Dave never having to save him. Meaning, John doesn't only warp through space, he can efficiently warp through time as well. Which means that once he gets his ability under control he will be able to take on Lord English. I forsee either Grimdark! John or Crockercorp! John somewhere in our near future, folks.