Something i didn't get about the ending.

At the ending of the novel the narrator ends up in a mental institution which he believes (or wants to believe) is heaven, and he says that Marla writes to him from earth and that "she says that someday, they'll bring me back", a bit after that he's talking to his psychiatrist (who he believes to be god) and it is explained that the mental institution is full of space monkeys (or at least the low-paying jobs), the question i had basically is, since he says that he doesn't want go back, not yet at least.
Is that supposed to mean that he someday (if ever) will be able to get out of the institution and have the posibility of being with Marla? Or is it supposed to imply that the space monkeys willl keep him there until Tyler returns (if he ever does)?.

Sorry if my question is too dumb, but it's just been on my head for quite a while.