Do we know for sure if they are going to not still air the episodes as a split season? Are they going to air in January? Also, they always air episodes til like the second Sunday of December and i doubt that is going to change. They didn’t skip for Thanksgiving every time either. We will see.
About the two hour finales, since they never have anything to do with the arc, i would rather they just stop.
It’s been confirmed several times that they’re doing away with Split Seasons, at least in terms of Split Season storyarcs: http://tvline.com/2016/06/11/once-upon-a-time-season-6-dropping-half-season-storylines/
Logically one would think that would apply to scheduling in some way, too. Channing Dungey, the new ABC President, has also said that she wants to do away with the very long winter hiatuses. I think preferably, she’d want OUAT airing new episodes in January and/or February.: http://tvbythenumbers.zap2it.com/2016/05/17/abc-2016-17-huge-in-season-hiatuses-may-no-longer-be-a-thing/
In regards to airing episodes in December, that could very well change, too. Some ABC shows have started their hiatuses at the end of November, so that practice could be applied to other shows. Also, it’s not the Sunday of Thanksgiving weekend that they skip, but the Sunday before Thanksgiving. This is because of the American Music Awards, which airs that Sunday every year. This has been consistent since Season 1. This years AMAs have already been confirmed to air on November 20th: http://www.theamas.com/2016/08/2016-amas-november-20/