Even though Nintendo has exclusive rights for Sonic the Hedgehog games on their console, it seems that Sega has much bigger plans for the future. Sonic might just be coming to the PlayStation 4 in the not so distant future.
Sega signed a deal with Nintendo to make the next 3 Sonic games exclusives for the Wii U and 3DS, Sega has already made 2 of these 3 games, which was the poorly received Sonic: Lost World and the fairly mediocre party game Mario and Sonic at the Sochi 2014 Winter Olympic Games. While it is possible that the next gen consoles might make Sega end their current contract with Nintendo, it is more likely that there will be another Nintendo exclusive title from Sonic this year and we will see Sonic on the PS4 sometime in 2015.
There is a new leaked game coming from Sega and Nintendo sometime in 2014, but Sonic will also be returning to the gaming world in the upcoming Super Smash Bros. game for the Wii U and 3DS.