One of the most anticipated titles for the PS4 has been delayed. According to directors Bruce Straley and Neil Druckmann latest blog on Sony  -
After spending so many years with Nathan Drake, he means a lot to the team, and telling the climactic chapter of his adventures is a task we don’t take lightly – this game deserves every bit of the attention to detail, precise pacing, and nuanced storytelling Naughty Dog is known for.Uncharted 4 was originally set to come out later this year.
So we’ve made the difficult choice of pushing the game’s release date. Giving us a few extra months will make certain that Uncharted 4: A Thief’s End not only meets the team’s high standards but the high standards that gamers have come to expect from a Naughty Dog title.
While the push is disheartening, these delays always mean more time to work out the kinks of the game and allow for a better overall experience.
The Uncharted series has been a strong franchise for Sony since its inception, with over 17 million in sales since 2012. 
 - IGN - Uncharted 4 Delayed Until Spring 2016 - http://www.ign.com/articles/2015/03/11/uncharted-4-delayed-until-spring-2016
 - Playstation.Blog - Uncharted 4: A Thief's End coming Spring 2016 - http://blog.eu.playstation.com/2015/03/11/uncharted-4-thiefs-end-coming-spring-2016-2/
 - VG247 - Uncharted Hits 17 Million Sales, UC3 GOTY Inbound - http://www.vg247.com/2012/04/24/uncharted-series-hits-17-million-sales-uc3-goty-edition-confirmed/