I have a feeling "chrsit will come again" is a big part of the reason. Dont' really know why just my thought.
If there was something atually wrong with the orignal and not a right way, I coud see changing it. But, I dont really ee the point. Maybe to be more "modern" language and more I guess the term is new age. I think peole want things to seem new ans fresh or differnt as opposed to traditional for some reason.
I could even see adding the other version undre it or tellign people that as a prayer to do. I don't really see a problem with the original though.
I'm not Catholic so I dont know if there have been many changes in doctrine and all that but I've heard htings are not quite ilke they were and changing a lot, that's probably part of it.
Doctrine has not changed one iota.
The problem with the words is not the words themselves, but where
they are in the Mass
The "mysterium fidei" or "Mystery of Faith" in the Mass refers not to Christ's death, resurrection and second coming, but to the Real Presence and the Sacrifice ofCalvary made present to us. The words uused to be just "mysterium fidei" and were in the words of consecration, or words of institution "For this is the chalice of my blood..."
They were moved out of there for dubious liturgical reasons and a response was made to them. In Latin it is still "Mysterium fidei" (Mystery of Faith) but they loosely translate this as "let us proclaim the mystery of faith"
It still refers to what has just happened at the altar. So the words "Christ has died, Christ is Risen, Christ will come again" are inappropiate here.