What is the Wisteria planted into? It looks like it might be a raised bed or something? How deep is the soil beneath, or is it like a pot, with a bottom? Trying to work out how much root room the plant has....

That wasn't a Wisteria prune, that was a severe hack down, I reckon. If you are very lucky it might recover & those buds might grow, however, it will take some time to get over being butchered like that. I find that plants have a strong will to live tho', so fingers crossed!

scrape a bit of the bark back with your thumb nail. if the stem is brown then it is dead if it is greenish then give it time.

If you ever have reason do something similar again do it in two halves so there are still some leaves left to support the roots. Hope it survives!

I just want to say that our enormous Wisteria here was cut back similar to this last year in early June, down to about 3 feet from the ground. It didn't do much last year, but its romping away now, so cutting it right down shouldn't have killed it - but insufficient root room might.