Actor availability issues mean we're unlikely to get a subplot about the Hatter frantically trying to find Grace in Wonderland, I guess. (If Stan hadn't been off doing MCU things, he'd probably have been in the spin-off already. In fact, I suspect the only reason Will exists is that Jefferson wasn't an option, which means that at one point Grace's mother might have been intended to be the Red Queen ...)

I think this makes it more likely that Hook's king is going to come up again, somehow, at some point. (Sure, Hook is hundreds of years old and his king should be long dead, but when has that ever stopped anybody in the Enchanted Forrest? I imagine villainous kings go in for immortality even more than most people.)