I am okay with this.
The Kindle Touch models, have the regulation touchscreen, organized by release date.
The Paperwhites, have the regulation frontlit touchscreen, organized by release date.
The Voyage and Oasis are special one-off models which don't fit as regulation-issue "paper-white" devices. (If Amazon wants to make them into a whole line, okay, we'll stick a number after them.)
So we can just keep on like that.
I doubt Amazon will release multiple non-frontlit touchscreen devices at a time, which is the only thing that seriously screws up our ability to keep to this path.
If people can't tell the difference between a KT4 and K4, I don't care. It is much less ambiguous than a K4-2 <-->K42.
tl;dr
Just tell everyone this is exactly what we intended.