Indeed, a segment during the show suggested that Sylveon was weak to Fighting and strong against Ice, much like the Steel type... but it's also affected by Poison in some way, which suddenly rules Steel out. So unless they're revising the type chart, then Sylveon may actually be of an entirely new type. The greatest irony is that this data basically contradicts any and all "leaked" info of a new type we've had, aside from a potential Poison weakness.
For the record though, a new type is still a terrible idea. I'm sticking by that. (Especially if Ice becomes even worse defensively...)