Hmmm, let's see...
Red/Green - February 27, 1996 (Tue)
Yellow - September 12, 1998 (Sat)
Gold/Silver - November 21, 1999 (Sun)
Crystal - December 14, 2000 (Thu)
Ruby/Sapphire - November 21, 2002 (Thu)
FireRed/LeafGreen - January 29, 2004 (Thu)
Emerald - September 16, 2004 (Thu)
Diamond/Pearl - September 28, 2006 (Thu)
Platinum - September 13, 2008 (Sat)
HeartGold/SoulSilver - September 12, 2009 (Sat)
Black/White - September 18, 2010 (Sat)
Black 2/White 2 - June 23, 2012 (Sat)
X/Y - October 12, 2013 (Sat)
OmegaRuby/AlphaSapphire - November XX, 2014
The list above are the Japanese release dates of every main series Pokemon title.
Considering that the past several releases have always been set on a Saturday, I guess November 22, 2014 is more likely.