Oh, c'mon. The new spoilers are about to come within the next hours and there's still talk about that hyped shadow figure for more than 30 pages?
What we do know about Akainu so far is that the silhouette acted the opposite - slept and acted carefree whereas Akainu wouldn't sleep, he'd be focused.
Ok, I see people didn't give my post the time of day, maybe you all though i was trolling or just trying to get a rise outta ya. Either way I'm still pretty confident that the shadow guy is most likely Marco from the white beard pirates. The first pic(with the teeth showing, idk who thinks its a pocket or a gap or whatever...thats just crazy you might wanna get ur glasses checked) of the face looking up just strikes me as Marco's style. Maybe people think it could be Jozu...not so....his body is clearly too bulky to be the man on the bird's head in the second shadow.
TO support my theory of it being Marco: (i don't know how to do the picture link thing, so if someone wants to do the leg work for me it would be appreciated, what else are you doing while you wait for the new chapter? eh? eh? moving on...) If you look at the initial chapter where the underworld brokers are shown (there are two shadows that resemble Jozu and Marco to me) i think Marco left their base...being able to fly....and then took a break on a bird(birds get along with a phoenix man right)...this is the best I got, wish i had the pictures to compare and prove. seriously i'm 100% on this....naruto is already out...op should be coming soon
Actually, in light of his post-timeskip look
After rereading Luffy's little chat with Monet about Joker with him giving Doflamingo the nickname "Bird Man", I start to think that the shadowy person might be some kind of secondary personality of Doflamingo - one that doesn't smile at all and only comes out when the usual Doflamingo falls asleep.
And I think his feather boa is probably a "smile user" being able to transform into a giant bird that is able to float on water.