A lot of people have been speculating "if" it will happen without asking "should" it happen.   

I'm going to take the "Maybe but probably no" side but trust that if it happens, they will cook.   

Not trying to strawman but the "yes" arguments seem largely hype/it will break the internet. And a lot of other "no" arguments boil down to "Aizen has more aura never revealing his mystery trap card".   

Zanpakuto is character writing. Shikai is the version of you that you show the world. Bankai is the inner version of you that comes out into the world. Old news. Prime example - Soi Fon larps as the perfect assassin the world expects of her with her Shikai but her inner self is temperamental and explosive, hence a big rocket launcher Bankai.   

Aizen's true self is an enigmatic contradiction - larping as the ubermensch by discarding his vices (what the espada represent) along with those connections and trying to stand atop, while also grooming Ichigo to meet him at the top where he's lonely and being relatively happy being brought back down once he has had time to reflect in Muken.  

**Whether Aizen gets to show Bankai or not is really whether Kubo wants to turn Aizen from an eternal enigma to someone with character development on display.**   

I will go so far as to argue that main series Aizen was too fractured and contradictory for Bankai to make sense. It would be almost less of an aura farm than a show of humility, that the time in Muken has given him clarity. His speech about courage in the end shows that this COULD be the case.

Should We Get Aizen Bankai in Cour 4?