3 cour is a lot, that's the total length of s1 + s2. I wonder how they'll adapt it, I think the Kraken arc was essentially the manga adapting a filler episode? So I'm guessing it'll skip that and be faster paced than s3, going something like
cour 1 - Seven Wonders + Illuminati (I can't imagine them advertising this first cour as the Illuminati arc unless they were planning to cover it in full)
cour 2 - Exam+ Aomori + the stretch of calm stuff after (finishing on the wedding)
cour 3 - all the Blue Night stuff
Since that'd mean they could do the rest of the manga afterwards as one final 2 cour season whenever it actually ends.