Eh, 3.3 seems like it's primarily going to be about the dragons, I wouldn't hold your breath for more of the WoDs in the main plot until at least 3.4, 3.5 more realistically. SE's playing the long game with them; remember that Elidibus was introduced in 2.1 and he hasn't even played an active role with our character outside of one scene until now.

I'm also in the camp that believes we're finally going to see a return of Hraesvelgr in 3.3. Middy though? Who knows - is he even still in our head or did he leave when he 'grew up' and declared us worthy of our title? This doesn't seem to be the case, since he was with us in the ARF.

He probably went back to Silvertear after making sure things in Ishgard went smoothly. That is his primary purpose, after all, he just can't go on adventures whenever he wants. I'm not sure he'll directly interfere with Nidhogg, even if Nidhogg directly calls upon him again, given Middy's seen what he's become.