YouTube is definitely not dead, but it is slowly losing popularity. Here’s a graph:
YouTube’s peak popularity was from October 2009 to May 2010. Then, there was a drop from June 2010 to December 2011, when there was a spike in popularity. A second drop occurred from January 2012 to December 2012, and since the beginning of 2013, YouTube has been slowly losing popularity.
It’s not dead though, which is good.