Thanks to Carnotzet for sharing this. According to Jluca, Russian Community Manager, in this post, Soviet Battleships will be coming in 2017. No informations at all if this is a full branch or just premium ships.
As always, please take this with a grain of salt, plans can always change so we can’t take this information for granted. It’s just one statement made by one developer and not an official announcement, before you get over excited and point the finger to anything Wargaming might change or do after.