According to the voice actor Nolan North, best known for his involvement in Naughty Dog's Uncharted as the lead Nathan Drake and as David in The Last of Us, has reported that a sequel to The Last of Us is currently in the works.
When asked if he was working with Naughty Dog on any future projects at MetroCon 2015, he replied "For now, [Uncharted 4] is the last one. I know they're doing The Last of Us 2, but my character in The Last of Us kind of met an untimely demise."
Albeit this does not fully confirm that a sequel is in the works, Troy Baker, the voice of protagonist Joel in The Last of Us, has stated that he knows nothing about a sequel. Baker says "I don't know if we're going to do another one or not. If we do, I trust Neil [Druckmann] and Bruce [Straley], and everyone at Naughty Dog to tell a story that needs to be told."
In spite of these news, I kindly ask no one to post any information about a confirmed sequel on the mainspace, nor create a page for The Last of Us 2.