I know the inclination is always "move up whenever there's an offer," but it's really not going to hurt Alex Rossi any to do WSR instead of GP2. The Air Asia team is not very strong, and I personally think spending time losing your confidence for a year isn't going to help. I'd rather find a way to save my money for the future (since F1 drives don't come free) and contend for a title in a series that's honestly not much, if at all, below GP2.
I also feel as though he has unfinished business in WSR. He has a habit now of impressing in winter testing, winning the first race, and then disappearing until later in the season.
But I also think he knows Tony Fernandes is his "in" and he'll have to see what Caterham would like for him to do. I'm not much of a fan of his, so I guess I'd rather him be in GP2 which I don't follow than here.