I'd say Maleficent is definitely one of the five then except that she doesn't really fit the sketch of the five Nomura did... Namine seems like a good bet given that she had that appearance in the concert. I mean, she obviously is still doing things and where else would she appear, haha.
The form of the figures in the sketch is not neccessary to "fit" anyone as the purpose of them is only to tease that there are "two more" beyond Ephemer, Skuld and Ventus that will play an important role in the coming events of KH UX.
I wouldn't count anyone as "definitive" just yet though as we can't possible make such a bold claim yet.
There are several possibilities though based on what we know about the nature of the world of Unchained so far and on what other teases we have been given from different sources.
I'm not sure why NOT put Maleficent there if she was one of the five, though, since if I remember correctly the end of Chi had already happened so it was known Maleficent would be involved? I wouldn't consider the sketches as solid information on the characters though, it could just be a random body drawn there, not really meant to invoke the people it's representing.
But if it's Roxas and Xion I'll just assume season 2 of KHUX is set inside Sora's heart and laugh.
Correct, that certainly throws a wrench into it reducing the probability of one of them being her.
Agreed, the sketches are just meant to invoke the visual hint that there are "two more" in general, not to actually hint at their identities or something similar.
Pfft, lol, in that case though it would beg the question as to how the whole bunch of keykids, Foretellers, Ephemer and Skuld made it into Sora's heart.
I really doubt it's Maleficent. She's already appeared in Chi, there would be no reason to exclude her from the anniversary art but show Ventus.
Granted, that's a viable point to make and may certainly also make the possibility of one of them being Maleficent less probable.
I'd still say it's more likely for those 2 figures to be new. Makes little sense to throw out Ven if the other two are also existing characters.
It makes sense if these two are supposed to be another surprise in the vein of "what are
those doing there". Ventus has been teased twice or thrice already and got people wondering and theorizing, possibly to get the ball rolling. When UX season 2 starts up and Ven finally makes an appearance people will craft further theories and while they're all still occupied with Ventus suddenly bam, another known character appears resulting in WTF reactions and even more theorizing and wondering.
That's fan reactions one won't get with entirely new characters.
Of course it is also possible that it is a split issue, as in one of the two is a new character (to complete the "cliché"-trio dynamic with Skuld and Ephemer perhaps) and the other an already known one as either a foil for Ventus or to give him someone to "play off" from and as initial support.
If it was even possibly an old character, I'd say Namine is a best bet. Take into consideration who these characters are. Some of this may sound like a stretch...
Skuld and Ephemer are both characters related to the Foretellers because of the Unions and Ava. The Land of Departure, from what we assume, is a world that exists because of the first Keyblade War and also was the home of Luxu's (now Xehanort's) Keyblade. The world itself likely carries many mysteries we've yet to unearth in the series and will come into play later on.
Ven sleeps within Castle Oblivion, and Namine was born in Castle Oblivion.
That's an interesting observation for sure.
According to Days Xion also originated from Castle Oblivion, so maybe it'll be both of them?
The fact of the scene from the concert implying that Naminé actually goes around somehow contacting the tormented ones may also play into this somehow.
---
Also, on a less serious note, what about when they actually decide to take the crossover with World of Final Fantasy up to eleven and the two unknown Characters are actually Reynn and Lann, coming instead of a Chirithy with Tama and Serafie? ;P