All anyone can go off is what's happened in the past and looking for the pattern of when new cards are released. So make what you will from this;
2017
2017-Apr: Titan XP
2017-Mar: GTX 1080 Ti
2016
2016-Oct: GTX 1050 Ti and GTX 1050
2016-Aug: Titan X (Pascal) and GTX 1060 3GB
2016-Jul: GTX 1060 6GB
2016-Jun: GTX 1070
2016-May: GTX 1080
2016-Jan: GT 710
2015
2015-Aug: GTX 950
2015-Jun: GTX 980 Ti
2015-Mar: GTX Titan X (Maxwell)
2015-Jan: GTX 960
2014
2014-Sep: GTX 980 and GTX 970
2014-Jun: GT 730
2014-May: GT 740
2014-Mar: GTX Titan Z, GT 720, and GT 710 (OEM)
2014-Feb: GTX Titan, GTX Titan Black, GTX 750 Ti and GTX 750
2013
2013-Nov: GTX 780 Ti
2013-Oct: GTX 760 (192-bit)
2013-May: GTX 780 and GTX 770
2013-Jun: GTX 760 (256-bit)
2013-Mar: GTX 650 Ti Boost
2012
2012-Oct: GTX 650 Ti
2012-Sep: GTX 660 and GTX 650
2012-Aug: GTX 660 Ti
2012-Jun: GT 640
2012-May: GTX 670, GT 630, GT 620, and GT 610
2012-Apr: GTX 690
2012-Mar: GTX 680
2011
2011-Nov: GTX 560 Ti (320-bit)
2011-Sep: GTX 460 (192-bit)
2011-May: GTX 560
2011-Apr: GT 520
2011-Mar: GTX 590, GTX 550 Ti, and GTS 450 (1GB)
2011-Feb: GT 440
2011-Jan: GTX 560 Ti (256-bit)
2010
2010-Dec: GTX 570
2010-Nov: GTX 580
2010-Oct: GTX 460 (256-bit) and GT 430
2010-Sep: GTS 450 (512MB)
2010-Mar: GTX 480 and GTX 470