Actually, I do think we could get that. There are multiple characters, who are/ were on the side of Darkness and are either helping Sora already or are likely to do it at some point.
On top of that, we don't even know yet if "Darkness" (Union Cross) is actually evil. We only "know" that MoM seems to be against it, if it is the same darkness he fought before. It helps Maleficent, but only because of this Sora & Co. were able to survive KH2 (battle in Hollow Bastion & the room before the top of the castle). Sure, we don't know if Darkness can also look into the future, but still, without it Xehanort would have won.
Also with the whole sin thematic on the side of the Foretellers, I also wondered if Darkness could have allies. I was mainly thinking about it, because of Demyx. He fits the describtion of sloth very well, but he used (or rather other used) his slothy, nondescribt personality to do good, although beeing alligned with Darkness. But I only have him at the moment for a Seven Deadly Sins (of Darkness) group, mainly because I have no other ideas how the other sins could end up being shown helpful and who could represent them. Luxord and gluttony (or maybe greed, but the former fits more to him, in my mind), since he loves to gamble, but for the other sins I'm very unsure, mainly because there could (and hopefully will be) some more new characters in the new saga and as I said unsure how they could portrait their sins in a better, more righteous way. But with the characters we already know...
Lust - no idea
Greed - also, no idea
Wrath - Lauriam, because of his sister? Or Elrena?
Envy - Isa?
Pride - all of the candidates I can think of for this are or were evil and are now dead. To be honest I could have imagined YX (yes crazy thought, but there were some minor details, because of which I thought he could turn against the plans of his old self), but then again his latest version was killed, so any time traveling tricks are out of the question (except when someone is still carrying around a Xehanort heartpiece... has someone seen Demyx?
). But Darkness itself could end up filling this spot, since MoM would be the Sin of Pride (of Light)