I think the writers just didn’t want to deal with future tech, while having an explanation for why everyone else in Storybrooke isn’t able to help out.
Except Snowing were already teased to be the ones to able to help. At least that is what the other article said.
There are different ways to help, though. They may not be able to come to the rescue (cause time travel) but they can offer advice to Henry, which is what I think their role is more likely to be
Actually according to another article, there is a picture of them both with the group as of right now. So clearly they are here o the rescue. Here’s the hint: http://ew.com/tv/once-upon-a-time-series-finale-photos/#a-storybook-ending
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