Players originating from the old USSR have dominated the Candidates the last years. In both 2011 and 2013 seven of the eight participants were born in the Soviet Union, while 2014 had six of eight (four Russians plus Aronian and Mamedyarov).
For 2016 Anand, Caruana and Nakamura are the three players to already be qualified, and the rating spots could go to Topalov and Giri. Then there will be two players from the World Cup (September/October), and one organiser spot.
Even if it could be the first Candidates ever without participants representing ex-Soviet countries, it is more probable that the event will be held in Russia, and many strong Russians also hope to qualify in the World Cup (Karjakin, Kramnik, Grischuk, Svidler). But the WC finalists could also be for example So and Vachier-Lagrave, or Chinese players.

Martin Bennedik's spreadsheet sorting out the way to the Candidates:
https://docs.google.com/spreadsheets/d/11U_0gAderuRhKuD2hr7GO_Ks9D3tX_v87ftKk2XN4zQ/pubhtml