Forgetting all of the other problems with time travel logic, Walter states that both he and Michael will be anomalies beyond 2015. I understand why Michael would be an anomaly, since he couldn't have been created by the Observers in the first place if they never existed, but I can't figure out why Walter would be an anomaly. Am I forgetting some critical interaction with the Obersvers he had? In this timeline, he and Peter were never saved by September, so it's not that ... so why would Walter be an anomaly?
I agree, this makes no sense. I mean for a time, Walter was going to let September accompany the kid... So if that had happened, would Walter STILL have disappeared in 2015? The whole thing just defies all logic.
That said, I still enjoyed it, on an emotional level. I am really, really going to miss seeing John Noble on my TV each week.