Empress Bulblax - Maybe? Don't know about this one. It might either be a small boss or a big buffed one
Burrowing Snagret - Of course this one returns.
Beady Long Legs - I think it's safe to say Beady returns after the reveal of another long legs.
Emperor Bulblax - Again, maybe. If it does, I think it will be a strong one again.
Giant Breadbug - Doubt it, though maybe the focus around food could bring it back?
Pileated Snagret - I think it's likely, but it might be a lot stronger.
Ranged Bloyster - I actually think this one has a high possibility of returning. Now with 3 captains, this boss may be easier but I think it could get a huge buff to be a big boss.
Waterwraith - Unfortunately, I don't think our old hatred frog-human thing isn't likely to return after the ridding of Purples.
Man-at-legs - Very unlikely, as less and less man-made objects seem to be on the planet at the time of Pikmin 3
Raging Long Legs - Not sure, maybe a new set of Long Legs replace these two?
Crawbster - Very unlikely. Not sure why but I just really don't see this boss memorable enough to return again.
Titan Dweevil - This is interesting: how would it attack? Maybe it's a toned down version like the Emperor Bulblax and will return and eat the Pikmin instead? I don't know.
Puffstool - Not sure, but I really want this to come back. I see this as a likely return, actually. It seems to fit with Pikmin 3's luscious setting.
Smoky Progg - This boss is memorable, but it's like a Pikmin Easter egg I really don't think will ever come back.
Armoured Cannon Beetle - I think this will. Don't know why, but I am thinking it will return along with its larva.
Goolix - Really don't think the Goolix will return, though its possible-ish.