They will just revise them all upwards by a percentage, it will take no more than a few keystrokes but no doubt a complete new organisation will be created to implement the change.
Proper revaluations for all properties is of course the only fair and equitable thing to do, were I living in a fair and equitable country I would be worried!
I will wait and see what transpires, I'm fairly certain that I will fall in the 80% who will no longer pay as my revenue de reference is only 29% of my actual revenue, if I will be exempt then a revaluation wont make me lose any sleep.
It might even be a trick to create a sort of amnesty, which would result in a proper revaluation albeit voluntary for lots of propertys, then they can just tweak the criteria so the 80% becomes 20%
I think this guy is a shrewd cookie.