Mike Judge was on NPR's Fresh Air, and discussed the actor who plays Peter Gregory in such a way that suggests there's no way they'd try to simply replace him. He does the character so well (balancing on a fine line of pushing the supposed disconnect from reality too far) that though you could replace him, you could never actually replace him.
Assuming the show gets another season (and I hope it does, I felt it started slow and had some problems but it's shaping up really well IMO), I suspect they'll have the character die - perhaps in a small plane crash, as has been known to happen.
Also, on a different note mentioned in the recap, I don't think the romance that is obviously supposed to be brewing is going to be typical in any way. I think the woman character does legitimately feel bad as she claimed to (and isn't just using him again), but there's no romance from her side. Though surely he's already misinterpreted all of her signals, as we're meant to expect from him, whatever happens I doubt will be groan-inducing which is the fear when romance is shoehorned in. I don't think it's shoehorned in here, is my point, and this sort of romantic confusion is undoubtedly typical in these settings.