As much as it's hated, McCown's been taken at the very least to give Hackenberg a chance to start, there's every opportunity that we don't take a QB at 6 and none of the big 4 will be left at 39.
People are saying that all these 4 QBs have their own flaws with Watson probably being the most ready to start. Trubisky has his lack of experience, Kizer had his own ups and downs last year and Mahomes isn't even close to starting and comes from Air Raid like Goff and Geno both did.
There's a high chance all of them bar perhaps Watson, will need to sit for the first season but the Jets have already done that with Hackenberg. It remains to be seen what good that has done as it's his mechanics and accuracy rather than the intangibles that he needs to work on, which is easier said than done.
If McCown starts this season, it's a damning indictment on Maccagnan's QB evaluation having traded up for Petty in the 4th, taking Hackenberg in the 2nd and then not taking a viable starting QB at 6 and that's without even getting into the Fitzpatrick/Geno debacle from last year.