I strongly suspect both XFCE and LXDE will wind up having the same thing happen, they both seem to exhibit evidence of being actively developed, which means bees could arrive in new bonnets at any moment :-).
Xfce has evolved rather than go for mad redesigns. Xfce today is certainly quite a bit different to much older versions, and it's migrated bit by bit away from its CDE style origins
The XFCE design process itself doesn't have a "lets write another new desktop and give it the same name" procedure, its a bit more evolutionary.
Alan