With 7.1 going on the PTR soon, and the data already being uploaded, we can get a sense of the Return to Karazhan dungeon.
Remember that all of this is just preliminary, and it's only about to start testing, and there could very well be missing pieces.
It appears that Karazhan will have a short attunement chain (presumably not as long as that for Arcway and Court of Stars) in Deadwind Pass.
So, the bosses (note, these could very well be out of order, especially if old bosses are in their usual places.):
Maiden of Virtue
Wikket (a Hozen-themed take on "Wicked?")
Westfall Story (West Side Story)
Beautiful Beast (a take on Beauty and the Beast, presumably the Disney version.)
Attumen the Huntsman
Shade of Medivh
Viz'aduum the Watcher
So, counting the opera hall fights as one, that looks like eight bosses, which either means they've scaled it down or there's one that isn't in the data yet.
I don't know about you, but I'm super excited to see this new take on one of the classics (and with no worries, as the old Karazhan will be untouched.)