After being traded, he definitely tests the market. The question is whether NO can offer a better place for him than anyone else at that time. In the mean time, your record will be better, which means worse draft position with whatever you're left with(2ND?) And you won't be competing for a championship. You just put your entire franchise at risk on a gamble that you can convince him to stay, and you have one full season to do it.
Their cap is going to be hard to play with. Really depends on what supporting cast they can offer while being of interest to possibly one more big name.
Unless you're in contention, which they're not, I can't see this as a steal at all. High risk high reward. If it works out, it'll be gold, but there are a ton of IFs involved.