Somewhere else is such a fun theory because you can just but john and martin into any game series/anime/ book/ what ever.
Like can you imagine john and Martin settling down in their new universe in the middle of the woods and Martin says something like "this universe isn't too different from ours! :D".
And then the look on john's face as he realizes in this universe Christianity was right and Mankind is dead, blood is fuel and hell is full.