Since the last CoroCoro didn't leave any space for another, theres a really good chance we only get 1 new Eevee Evolution. I know I'm just repeating myself, but we don't have to have more than one show up. If Sylveon is Dragon Typed, the chances its the only new one is really high. If another type the chances lower, but since CoroCoro didn't leave any other hints and the fact that Sylveon is being showcased by itself is a pretty good show that its the last one for now at least. Though if Dragon, pretty sure its the last one altogether until a new type comes in.
Also pretty good chance that if Normal, its the final since Eevee would have found its original evolution method/final evolution method.