I'm digging the polar bear theory, but I don't see so much how that would keep Alpert young. I had my own idea on how all of that worked after the last Locke episode...
Excellent season. The finale didn't hit me as hard as the third's, but as Roto said, it's hard to be shocking when the whole season's been plotting what happens directly afterward. I'm really looking forward to seeing how they handle the next season with the cast split in two.