I based episode five on the black lion store release cycle and under the assumption that it wouldn’t release concurrently with Wintersday. We could end up waiting until next year though.
Wintersday’s date is based off previous years.
Edit: Wintersday will likely end on 1/8 but I don’t see them releasing the episode then. If it doesn’t release this month then I see 1/22 being the next best date.