So, here's some people that could potentially wield a Keyblade for Kingdom Hearts III:
1. Xemnas- Nomura stated in an interview that it was possible that Xemnas was 'intentionally' not using a Keyblade, which could prove to be a threat in Kingdom Hearts III if he decides to use his.
2. Namine- Namine is the soul of Kairi and the body of Sora (tell me if this is the other way around), and if she's parts of two Keyblade wielders, maybe she could dual-wield in a time of trouble. While I highly doubt this, Namine with even a single Keyblade would be EPIC.
3. Yen Sid- Yes, he's already a master and has a Keyblade. But he's RETIRED. I'd just love to see him pick one up for Kingdom Hearts III and show Xehanort who's boss. I mean, Yen Sid kicking Xehanort's ass in the final battle? THAT SOUNDS AWESOME.
4. Xigbar- With the curiosity of one day wielding a Keyblade already (from birth by sleep, I believe), Xigbar already wants his hands on one. I mean, that's why he teamed up with Xehanort to begin with, right? If he gained one for Kingdom Hearts III, I think things would get much more interesting (plus, if he didn't get one, he would probably ragequit and blame it on Xehanort, making an interesting betrayal story).
5. Donald and Goofy- okay, never mind. This is a stupid idea. But I guess it would be cool... they probably could wield if they wanted to, right? They have hearts of light, after all... But it would ruin the staff and shield thing they have going on... dumb idea.
6. Oswald- OKAY NEW CHARACTER TIME! I'd LOVE to see this guy make a cameo in the third game as the Rival of Mickey! Just thinking of Oswald being that makes me excited!
7. Finally, we have Xion. If she's going to return, she might not have a Keyblade since hers was an imitation... she'll probably need another one, in the end.
So, what do you think about my ideas? comment below.