So far, every veteran revealed via the site has coincided with a Nintendo release.
So I took a look at some upcoming releases and paired them with possible character updates. This includes potential newcomers:
Chibi-Robo Photo Finder (January 9, 2014): Chibi-Robo
Kirby Triple Deluxe (January 11, 2014): King Dedede, Meta Knight
Donkey Kong: Tropical Freeze (February 2014): Diddy Kong, Dixie Kong, K. Rool, Cranky Kong
Professor Layton and the Azran Legacy (February 28, 2014): Professor Layton
Mario Kart 8 (Spring 2014): Yoshi, Toad, Wario, Waluigi, Baby Bros.
Yoshi's New Island (Spring 2014): Yoshi, Baby Bros., Kamek
Obviously there are other games too that might see some newcomers/veterans revealed but have no definitive release date yet (Hyrule Warriors, Yarn Yoshi, etc.)
I also didn't take into account releases in other countries; Japan saw A Link Between Worlds released today, which is why Zelda was revealed today and not in November; this might be a factor too.