So i cleared the Skyborn Altar much earlier today learning a word and killing a dragon there. It's probably been a week or less in game time. I revisited the sight and there is a dragon there! So, i kill that dragon loot his bones, scales, and his 200 gold but... but... i absorbed no soul, and he didn't burn in the epic way dragons tend to. I'm not complaining about this at all, in fact i actually like this since people won't be able to "game" soul acquisition in this manner anyway.

Just thought it was something interesting to note.

Yes, it seems that respawmed dragons will not give you new souls.