Do you think Riku will fight Sora again?

Don't be confused, Riku's fight was against Ansem SoD not darkness in general. You can see with the endings of CoM and KH2 that, while he is a denizen of the light and that is where he wants to be when all is said and done, he doesn't fear the dark and is willing to use it if that is needed of him.

 

But what exactly did Ansem's machine do to Riku? Destroy the remainder of Xehanort's Heartless in him or the remainder of his darkness (hence why he couldn't open a corridor of Darkness later on)?

 

i hope they do, their rivalry was what made the first game and chain of memories pretty interesting. i think they will have a fight again but most likely not a "to the death" kind of fight because it seems as though both characters have patched up their relationship with each other and learned from their past mistakes.

 

Possibly. Like Terra and Aqua fought each other, but it was only for a test. So unless if Riku turns back to the darkness, the only reason I think why Sora and Riku might fight again is because Yen Sid is testing them.

 

I don't think Riku would turn on Sora again because he overcame the darkness. He might still have it in his heart but he'd fight against it again to help Sora and such.

 

I always thought it might be like a test, as many have already said, where Yen Sid (or someone else) is controlling it and sort of manipulating Sora and Riku in order to teach them a lesson. Like they fight in the end over something but then everything is revealed. Or they could just fight as a sort of spar but I don't think they'll be on opposite sides again since that has already been done and audiences don't like to see best friends fight too much.

 

I think that since the whole theme of KH 3D is "trust" I think there would be no reason for them to fight unless the trust is between them and their Keyblades. Although like someone else said, Riku still has Darkness so who knows. Personally I hope they do.