After seeing DX12 on Star Swarm, I can't see Mantle surviving. I think even Richard Huddy knew this way beck when OcUK asked him questions and his reply was "Mantle is there for as long as it is needed. We don't have an emotional attatchment to it and if developers don't care about it, we will put it down and walk away".
And when you look at the future Mantle games, it doesn't look good.
http://www.amd.com/en-us/innovations/software-technologies/mantle#games
The only addition there is BFH. I feel AMD shot themselves in the foot with Mantle as well by not releasing a public SDK and only allowing select devs access.