The team is scheduled to have approx. 65m in available cap space this offseason. I'm guessing there's a decent chance they'll be carrying some of that into 2018, where the cap will go up even more.
There's no reason to believe that they can't carry a tag/trade salary for a couple weeks, should they choose to. They may want to wait another year while having a solid backup before making a decision, and it could also allow them to showcase JG for another preseason. I'm not saying that the odds of this happening are great, but it shouldn't be automatically dismissed, either.