A close comparison of the two pictures posted by dingyibvs, reveals that in the 'new' tank, the reactive armor arrays cover up even those portions of the top of the turret where the thermal imaging sights, machine guns, sensors and countermeasures are mounted - whereas in the 'older' tank, these are in effect, exposed.
The degree to which this has taken place is responsible for what appears to be a new wide channel (a space free of reactive armor blocks) immediately in front of the gunner's sight, in effect changing the whole appearance of the turret.
That being said, it remains to be seen whether the turret is in fact physically larger, and the new appearance is not just the result of a set of redesigned and re-configured reactive armor blocks.
This is indeed my suspicion, that this 'new' design has more to do with more extensive coverage by reactive armor (protecting the whole turret roof - against 'top attack' munitions) than any major physical changes - notwithstanding relatively minor upgrades like the much larger gunner's sight, etc.