Facebook[1] and Google[2] have both publicly stated that they are using Mercurial internally, so "near death" seems like an exaggeration. Mercurial has some significant advantages over Git if you want to implement a scalable backend for really large repos.
[1] https://engineering.fb.com/core-data/scaling-mercurial-at-fa...
[2] https://cacm.acm.org/magazines/2016/7/204032-why-google-stor...