Highly unlikely, because Master Xeharnort has been looking for either empty vessels like the members of the Orginization or those who have their hearts filled with darkness and easy to take over. If Xeharnort wanted to take over the Disney villians he would've when he had the chance when Ansem SOD was around them. But I think he saw potentinal in Riku because Terra gave him the power to weild the Keyblade, and when Ansem saw this in Riku he thought he would be a suitable vessel. But unfortunately Riku became resistant to the darkness and will not let Xeharnorts heart take a hold of him, instead only a shadow of Ansem was left inside him to become his darkness to control.
Terra was under Master Xeharnorts control because he was leading Terra into a false sense of secruity to the darkness so he would have a new vessel to further his plans. Despite the fact he didn't take count in Terra's own heart embound with his armor still lives on. The other members like Sai'ix and Xigbar had taken Xeharnorts heart before they were defeated. So far we only have 5 vessels that we know of now (Young Xeharnort doesn't count because he will become what he is today, unless that is Terranort again because thats what Young Xeharnort looked like when I first saw him. And if that was Terrahnort, disregard this message).
The other 7 we don't know of yet and also it's unknown that if Master Xeharnort still wants Sora as his 13th vessel or if he'll choose another person in the time being. Also we don't know if all the members of the Orginization were taken over by Xeharnorts heart because we only saw Even, Leadus, Ezion, Lea, and Dilan come back as humans. We don't know if Demyx, Larxene, or the others were taken over.