I think it’s good to have a grasp of what features those technologies could bring to a game engine and the benefits your games could make from using them. Remember that games are an ultra competitive business arena so if there are any advantages you can gain from adopting new technologies you need to know about them.
Mantle is shaking up the industry as already OpenGL and DirectX are having to adapt and evolve to match it’s performance improvements.
Mantle aims to reduce the CPU overhead of the rendering pipeline and allow multi-threaded rendering. So it takes advantage of modern multi-core cpus and powerful GPU’s*.
*Currently only for the latest AMD GPU’s.
It looks like Crytek are going to use it in their engine and the Frostbite engine (Battlefield, Thief, Plants vs Zombies) is already using it.
But it’s good to see that DirectX 12 and OpenGL are going to provide a similar solution.
Hopefully Unreal will adopt it as well, at least in the interim until Dx12 is released.