I guess we shouldn't expect an update for TBC or even WotLK? I've been looking at the addon to maybe update it for TBC but I'm stuck on retrieving the data for TBC

That would be good.

Looks like Buffet is being actively maintained: https://www.curseforge.com/wow/addons/buffet

Sorry, I don't have any intention of updating this for TBC. I haven't played WoW at all for quite a while now, and don't intend to come back any time soon.

I originally got the data from scraping classic.wowhead.com using python & selenium. If you're interested, I might be able to help you get the data for TBC in the format that this addon uses.