It is the nature of development. While they are working on many aspects of the various changes proposed, each one will be ready when they get it to the point of release. They don't want to list all the changes coming for 2.5, 2.6, 2.X as they like to be flexible. If a change planned for 2.5 is not ready yet, but everything else for that change is, then they would probably go ahead and release 2.5 as is and push the one item to 2.6.
Even if they communicate out a tentative schedule of changes, people will take it as gospel and instantly complain about it missing when they were to release the latest version.
And there is always the possibility that something that sounded great during discussion turns out a dud when they make the implementation. At that point, they will go back to the drawing board and revisit / revamp the change. I do that all the time I come up with what I think is a great idea for 7 Days to Die and my playthroughs, only to find out that it didn't work as expected or was not as fun as I originally thought (and with it being a personal mod of mine, I am the only customer that matters and those things still happen).