hmm.... did they speak all of it or just parts necessary to convene with dragons/priests? maybe months were needed then.

I presume they (especially the dragon priests) would have spoken it fluently.  Like the Catholic church performed mass in Latin, they probably would have performed ceremonies and rituals entirely in the dragon language.

true

Are we ok with just saying "Sadonvumme" for Greybeards? I am, just wondered if anyone had a desire to make a separate word. 

I almost feel like there should be a separate word, but the question them becomes what they would call themselves (they have taken to calling themselves the Greybeards in Cyrodiilic).  "Thu'umiik/Thu'umaaniik", "Voiced Ones"?

I like that

Hmm, is -iik the best way to make "Voiced One"?

"Engl. "-er", modifies a verb into a noun that is a doer of that verb."

"Voicer"?...

what about 

Ver-  

"Modifies a noun into an intransitive verb meaning "to make or create"."

Verthu'um/Verothu'um. "Voice Maker"

or

-dein / -ein

"Engl. "-ship", expands the meaning of the base noun. "-ein" is used if the last syllable of the word contains a "d"."

Thu'umdein. So like "kingship" (the act of being king), "relationship" (the act of having a relation), "Voiceship" (the act of having Voice) ?

Now that I think about it, perhaps "Voiced Ones" would be more than just Greybeards, but perhaps Tongues.

Maybe Greybeards should be "Followers of the Way" or "Way-Followers", "Zen-Kiibokiikke" (ugh).

("Zensethu'um" means "Way of the Voice".)

Way-Voice, Zenthu'um.

Way-Voicer, Zenthu'umiik.

*shrug*

Perhaps "Sadonvumme" might be best if only for simplicity.  Also, I made "Kiibokin" for "follower" because "Kiibokiik" is quite messy.

Sadonvumme it is then. I'm fine with that.

You are correct, dragons are genderless, although that doesn't necessarily mean they don't understand gender as a concept.  There are two possibilities, one is that gender was in the language to begin with, or two, it got injected into the language once the ancient Nords started speaking it.  At any rate, they have pronouns "he" and "she", and gender-specific words like "king" and "queen".