WZ-111 5A= Rumor. No comment from WG about its existence at all. Personally, I wouldn't get too excited about something until WG at least acknowledges it. You're just wasting your time if you do.

XM 551, aka the Sheridan, will be a Tier X American light tank. We do know that it will be around in public matches in 6.5, some testers will get the chance to mess around with it. From what it sounds like, it'll be able to fire both conventional shells and missiles, and that ATGM shells will be the premium shell, along with APCR as its standard and HE shells as the third option. Personally, I think being able to choose regular shells and missiles is kinda OP, and this is why WG is testing if having ATGM shells as a premium shell is gonna work out or not. My guess is that the shell will be replaced with a higher pen, lower damage HEAT shell if the ATGM ability proves to be too OP.

Chimera has been mentioned by WG in a teaser. It's basically a Caernarvon with an IS-X gun (aka 120mm). I say an IS gun and not a capitalist 120mm gun because apparently the accuracy is really bad. Rumor is that it comes out in 6.5, and my guess is that it will be released in crates first.

Let's also not forget about the Centurion Action X, which WG did mention is currently in testing right now. No speculation on when that will be introduced to the game.