This scene was in flashback mode, so it could be some form of confrontation, or perhaps they were working together in some capacity. It’s been far too long since we saw them in the Enchanted Forest together (usually it’s just their Storybrooke counterparts), so this is bound to be exciting... and dramatic. Plus, the writer notes that this was the same location where Snow discovered all the dead villagers in Season 2 with the Evil Queen.
As for the Lost Boys, they were just strolling around and not filming, but reportedly Colin O’Donoghue (Captain Hook), Jennifer Morrison (Emma), and Lana Parrilla (Regina) were all due on set later that night. Could they be uncovering the boys’ Neverland hideout? Finding Henry? So many questions.