Like all my last posts have been about who's going to show up in KH3, but I never thought about 2.8 (technically it is 3 cuz its "prologue" which is the intro).

From my point of view, the hype is all about Ven and his awakening (ITS BEEN LOOOOOOONG OVERDUE.  But from previous encounters, there should be another Final Fantasy character that will show his/her face.  In KH1, it was Leon/Cloud and friends.  In KH2 Its Auron.  In BBS it was Zack.  So who is the next guy/girl?  I don't follow Final Fantasy as much as KH but my guess would be maybe Lulu (idk)

 

But there may be an intro to some more Disney people (ofc there is duh).  My guess is Frozen world and that thing with the Reck it Ralph.

 

And ofc I have to talk about this - one of the 4 missing nobodies

I think that Demyx's somebody will appear.  Demyx overall is a fun character and I think that it would be really nice to see him.  Plus his element is water and Aqua's name is Aqua - water, get it 

Well, I'm not really sure about who we'll see in 2.8, but honestly, for the most part, I think all we'll be seeing are illusions that Aqua comes across. Like you said, there seems to be a strong focus on Ven, as previous footage of the game seems to put a special emphasis on him! Perhaps we'll learn something new regarding his character! We'll probably see illusions of Eraqus, Xehanort, and the people Aqua has met! But I don't think we'll see a new Final Fantasy character, since I'm pretty sure the focus of the game will be put majorly on Aqua and Mickey, ya know? But who knows? We could be surprised!

Well, I'm not really sure about who we'll see in 2.8, but honestly, for the most part, I think all we'll be seeing are illusions that Aqua comes across. Like you said, there seems to be a strong focus on Ven, as previous footage of the game seems to put a special emphasis on him! Perhaps we'll learn something new regarding his character! We'll probably see illusions of Eraqus, Xehanort, and the people Aqua has met! But I don't think we'll see a new Final Fantasy character, since I'm pretty sure the focus of the game will be put majorly on Aqua and Mickey, ya know? But who knows? We could be surprised!

Well remember, it is the introduction to KH3 so it has to include something.

Even if 2.8 is the prologue to the final story which is KH III,I don't think we'll be seeing any new character, KH one or FF one . We will probably see new enemies(heartless) and also a lot of Aqua

I doubt we will see any new FF characters in 0.2. The focus is on Aqua and King Mickey. Why would Demyx's somebody be in the ROD? How would Frozen and Wreck it Ralph even be in the ROD? Back Cover is a movie and the only world you'll see is Daybreak Town, whilst DDD isn't getting anything significantly new.