Possible Spoiler, but an UPDATE:Don't read on, if you'd rather find out yourself, but...
I just cured myself of Vampirism using Falion's ritual and the black soul gem.... I had Serana with me the whole time. As soon as the ritual was complete, and I was cured, I talked to Serana and an option is: "I want you to turn me into a vampire".
I'm only in the beginning of the Dawnguard quests, so... here you go if you're a vampire and you want to change the way you look, and then become a Vampire Lord again!
Confirmed. It works perfectly fine.

Hope I didn't spoil anyone!