The tier X LTs are getting buffed, as they are (unsurprisingly) underperforming. There will be a generally small increase to their ammo capacity and (with the exception of the WZ-132-1) either a damage buff or a RoF buff. The Rheinmetall Panzerwagen gets a few more changes, namely its alpha damage gets reduced in exchange for major gun handling and rate of fire buffs.
Source. (4th post from the top)