Sony supposedly has a policy of not offering games through PS+ IGC if they've been on sale recently, presumably to avoid the backlash from a lot of people that would certainly happen if they dropped the price as an incentive to get people to buy the game, then turned around and gave it away for "free" a week or two later. So while Second Son will likely be an IGC game at some point, it being on sale now probably means it won't be in the next 3+ months. They'll probably offer games like Killzone, Knack, Journey and a couple of 3rd party games like Tomb Raider DE, Need For Speed and Assassin's Creed IV as bigger IGC PS4 games in the coming months.