More Henry and Rumple bonding in particular is something that many of us had been asking to see more of.
This
There are also more classic literature they could pull from, like they did for the Land of Untold Stories subplot.
And This
Exploring dropped storylines for several recurring characters.
Or exploring some characters in more depth like Archie, Grumpy, Red, Granny, Nova, Maleficent, Lily, etc.
I am most excited for new characters, new stories, and new people to care about. I would have loved if they had not brought back any of the old character regulars, but I am excited to see how this all works out.