[2021] Completing King of the Sea collection

Yep!
You can collect KOTS containers this season just like you could the previous two seasons.
Dates and times are listed here: https://worldofwarships.eu/en/news/general-news/stream-rewards-0109/
You can ALSO get your hands on three more in the armory for Community Tokens.

It has to be during the KOTS streams listed in that article.