If you notice the tournament rules, restrictions were removed as a gen comes to an end.

2003: gen 3 pokemon only
2004, 2005: National dex, no legends
2006: National dex, legends allowed

>Jump to gen IV

2006: Sinnoh Dex, no legends
2007, 2008, 2009: National dex, no legends
2010: National Dex, legends allowed

>Jump to gen V

2011: Unova Dex, no legends
2012, 2013: National Dex, no legends

>Jump to gen VI

2014: Kalos dex, no legends
2015: National dex, no legends
2016: National dex, legends allowed

As you can see, every time box legendaries are allowed, a new gen follows. Considering this year's rules, we can expect gen 7 games in 2016.

http://bulbapedia.bulbagarden.net/wiki/Rule_variants#Pok.C3.A9mon_Video_Game_Showdown_2008

Hate, meme, deny, screencap, etc, don't get mad when I say "told ya" in 8 months.