Facebook is unlikely to be overtaken by another fully featured social media service for the forseeable future.
however
score: 3
if something replaced the need for an internet connection to connect people's profiles around the world, well...nevermind Facebook would probably already be on top of that.
Facebook, while becoming less "cool", is so integrated into many societies that it has become more of a utility, to the point that not having one is on the level of not having a key device, such as a smart phone. In order for it to die out, many of the current users would need to die, or move enmass
It is so ingrained not only in popular video games, other social medias, and above all else it is a reliable, widespread form of communication between people who under any other circumstances wouldn't be able to connect.
The role of facebook will likely never be replaced. However, depending of how facebook changes their businessmodel or their terms of service, some other provider may give us an alternative to facebook