So they will make a new chain... with full control over that chain?! Some board of directors, or politicians, will have the power to do with that chain as they like? Like to issue more coins when they like, they will burn some coins, or sell where they wish?!
Isn't all that what we have now?! Of course, as others say, controlling digital will be much easier than controlling cash! So new digital fiat will be fiat, with more powers...

Well, what else to say here than to state the obvious... centralized is centralized in any form! With a digital system, centralized organizations will have more control than they have now... on the other side decentralization is something else! And we will see what will people choose... in the end choice is on us! All of us!