Fernie, it seems no one knows the answer as to the fate of the Everyman and Azed puzzles once the sale goes through. I imagine that crosswords are fairly low down on the list of things to sort out when selling a newspaper.
It’s fair to assume that new Observer puzzles will sit behind a paywall of some sort, but your question as to the archive of old puzzles is an interesting one. Perhaps they will stay with the Guardian and be freely available. Let’s hope so.