In my best Bill Clinton imitation, that would depend on what dead means.
SOSUS as a program no longer exists, so in one interpretation SOSUS is dead.
However, IUSS (Integrated Underwater Surveillance System) is alive and doing well.
The Navy being what they are, and the underwater surveillance people being what they are, there is naturally not a lot of public information on the IUSS.
After Walker, this type if information is strictly limited to help prevent another Walker/SOSUS incident.