Remember when last year they teased us with the T-62M in the multithreading video? It could be an updated model for it, I was reminded when I saw u/splinterfoxhound suggest it could be the T-62M due to the round cylinder on the back of the turret, which the T-62M does have in pictures. I do agree that this image does look more like a T-72 to me, but unlike the T-72, the T-62M does at least use a hull currently in the game AND we have seen the T-62M show up in an easter egg before. It seems like way too modern of a package to be in the game, but, well, it's the best idea I have got.
Source: https://www.reddit.com/r/WorldofTanks/comments/ecisxb/i_think_i_figured_it_out/