WG is currently working on another tank game outside of WoT. You can verify this in the NDA supplied through their request to playtest. It has been advertised through Facebook and the video supplied is the one of two used. I cannot find the second video through search engine. The one included can (Used DuckDuckGo). Here are the links:

Site to enter playtest:

https://projectcw.dev/

Video:

Also there is a project that looks similar to mechwarriors in closed alpha:

https://steelhunters.com/

You can apply for the closed alpha here: https://survey.steelhunters.com/s3/sh-playtest-applyfirst-march

UPDATE: Videos got taken down by Wargaming. Linked reuploads instead.

You might remember Excalibur, we had a post with its logo 2 years ago. WG Seattle was making this until it was shut down and the project was transferred to Minsk for finishing. Looks like AW with Heliborne to me. However, it might kill Armored Warfare.

Unfortunately, the original videos were removed from YouTube by WG.

My fellow commenters have revealed pieces of old info, and it seems that WGs secret project is most likely Total Annihilation 2 (Chris Taylor is working on that), not Excalibur. Honestly, Excalibur is a whole new thing and nothing at all is known about it except what was leaked. It is unknown what WG is really working on, and we will see soon.