In all seriousness i understand your woe and dont think it will be an issue.
You just have to see the amount of changes made during the last patch to Dk to see that Blizz are still developing the DK class.
How things will pan out...who can say.
But lets face facts. The DK is a "hero" class. Now i know there is a lot of debate about what this actually means and im still undecided myself.
However the DK can and does "fit" the hole in the raid whereby i need a dps but i actualy need a possible further tank. So im looking for a class that has high dps BUT can alos act as tank.
Even if i take a full "tank" spec DK to a raid and ask him to go dps on this fight...he is quite easily outputting more damage than a prot warrior would in the same position. A pally tank can but has to watch aggro and the druid can go pussy and still put out some serious dps. We have even had our MT druid AOE tank trash as pussy....
I suppose what im saying is your class is valuable yes. its also very viable in many situations and you can be rest assured you will always have high dps in an OT role and be quite appropriate in a MT role.
class buffs/nerfs and adjustments will continue...gear will change...mechanics will change.
I wouldnt worry..it looks like DK are Blizzards new best friend and im sure you will be for the remainder of WotLk as the storyline and lore revolves areound you a lot more yet.