I personally would like Tony to come back as his old evil self. I can see him revealing he was never on the island and that he brain washed a Dimera underling into believing he was Andre.
I would love it if he pulled that and I think it would be possible from what I understand before "Tony" went bad he was friends with the people he would later consider enemies. I can see him wanting that back and concocting a plan to do so.
I can also see it blowing up in his face with his supposed death.