We have heard talk over on Reddit about a leaked document that suggests that there is a tech demo on stage at the E3 for Uncharted 4: The Sunken Blade. But at the same time you do have to take things with a pinch of salt as it would be a departure from the typical naming convention.
One user pointed out that “There is no series naming convention. Yes, Uncharted 1 and 3 had “drake’s _____” but Among Thieves and Golden Abyss didn’t follow any patterns.”
Another user said that they posted the same thing and then took the post down when they found it was faked. While others wanted to know where the location of the leaked was and what the source of it was.