Zoroark was clearly an attempt by GameFreak at duplicating Lucario's success at acheiving popularity through a movie despite not being Legendary.
It failed to become the next Lucario. Still, it is considered one of the most likely and plausible candidates of the newer Pokemon.
Victini is no slouch either, with getting a boost due to being Masuda's favorite Pokemon, which could potentially influence Sakurai if he goes to GameFreak on any newer Pokemon to consider. However, its support died down shortly after its movie, possibly because the initial feelings of it being a potential character faded away, and thus Victini became a "Flavor of the Month".
Meloetta is the next Flavor of the Month after Victini, due to Keldeo's overall lack of support as a playable character and due to the anime, where it became a recurring character for an arc.
However, like Victini, this is fading away, especially now that Meloetta's part is over. To be fair though, it never really got off the ground like Victini did.
Now we move on to the clear choice for the next Flavor of the Month, Genesect.
What is most interesting about this one is, it had been revealed and has events for it numerous months PRIOR to its movie, so its clear that GameFreak is trying to hype it and keep its popularity high. So while it may end up being a Flavor of the Month....it's going to be a very long "month".
So, if a newer Pokemon is to be added, it's going to be between Zoroark, who didn't quite fall into FotM status, and Genesect.