The main problem I can see here is that according to the rules you can't create vampiric dragon because you can create vampires only from humanoid and monstrous humanoid.
But if you really want to do that. I don't think that they should get next age level because they are undead so what is age for them?
Draconomicon update:
FWIK dragon gains its age levels because its type is Dragon. In the Draconomicon there is this note that:
Size and Type: The creature’s type changes to undead, and it loses any subtypes it had in life.
So I am still convinced that the dragon is not able to age anymore.