We have to remember that Turbine will use the enhancement upgrade to also revamp the classes. Some classes like clerics and paladins really need an overhaul.
I think Turbine already have the technical part of the enhancement upgrade mostly done. It will be a more advanced version of the one currently used for epic destinies. The hard part is to put the abilities into each tree.
What takes time is to fine tune the abilities you can get in each tree.
Seeing that cleric domains have shown up prematurely on Lamannia shows that Turbine are definitely working on the new enhancement upgrade. I guess clerics will be boosted with cleric domains in their available enhancement trees.
I believe it's important that Turbine take their time to get the balance pretty right so all classes get a chance to shine, even at epic levels. I want the enhancement update to work well when it comes instead of having serious flaws so some classes get the short end of the stick again.
It could have been fruitful if Turbine could present the different trees with abilities so they can get feedback on them before implementing them. Players can come with invaluable feedback regarding balance similar to what was done when the combat and spells system was changed for MotU.