This thought crossed my mind especially after reading a few Fanfiction but do you think we may see the Nobodies of Disney and/or Final Fantasy Villains (isn't Sephiroth Cloud's nobody he's probably Cloud's heartless though since he said he is the embodiment of his darkness) in KH3 or future titles

The closest that the series has come to doing that is when Scar turned into a Heartless, but I doubt that anything similar will happen in the future.

This thought crossed my mind especially after reading a few Fanfiction but do you think we may see the Nobodies of Disney and/or Final Fantasy Villains (isn't Sephiroth Cloud's nobody he's probably Cloud's heartless though since he said he is the embodiment of his darkness) in KH3 or future titles

Disney Nobodies maybe...Final Fantasy Nobodies? Never. The series has become too-Disney oriented so nobodies for FF characters are never going  to happen. 

Axel is probably the closest we will get to a Final Fantasy nobody

Plot Twist: Larxene is Elena's nobody.

(Don't care if we're missing an R)

Disney Nobodies maybe...Final Fantasy Nobodies? Never. The series has become too-Disney oriented so nobodies for FF characters are never going  to happen. 

"Become" Disney oriented? It's been completely Disney oriented since the BEGINNING.

Hmm, I'm not sure . . . .  Are there any Nobodies now that Sora released all those hearts at the end of KH2?