XY reveal timeline as a reference (might be a day or two off/some mons might be missing):
1/08: XY Reveal, starters and box legendaries
2/15: Sylveon, 2013 movie and short aka first look at Mega Mewtwo Y
5/15: Region, protagonist, Helioptile, Fletchling, Pancham
6/11: Release date, fairy type, Noivern, Vivillon
7/13: Inkay, Pangoro, Malamar, Swirlix, Spritzee, Clemont, Bonnie, Team Flare, and other stuff
8/09: Dedenne, Skiddoo, Bunnelby, a bunch of Mega Evolutions
Bunch of Pokemon and Megas in the September corocoro release. Also the new type chart.
Seeing as nothing happened in March and April 2013 there is a possibility we won't get anything new for a while here either.