My sense is that if Cheney leaves that he will be gone and not step into a more stressful job..... jmo. Cheney deserves to be able to kick back and do what he wants now and I guess that could entail another cabinet job, but not my guess.
as long as he is working closely with W, I guess I wouldn't worry...but I like him and I think his wife is great, too...there's a couple who have put some very fruitful hours into their lives...