My first thought when I saw the slides, especially the "cross-platform part", was "yay, no more DirectX!!!". This might mean that we're finally going to have AAA games on Linux too (DirectX was a big obstacle to that).
Mantle still doesn't solve input, audio, and a number of other services that DirectX provides in a unified way. Also, potentially AMD only, which has a smaller share than both Intel and nVidia.
I'm not sure that matters too much, to be honest. Mantle probably isn't coming to the consoles because they have their own direct architecture.
If you develop for PC you want to maximize market share so you need to ask if it's really worth supporting another graphics API for a performance boost on the #3 vendor.
Both old and new AAA games are on Linux today. Tribes 2, Descent: Freespace, Brutal Legend, Psychonauts, Natural Selection 2, HL2, TF2, Unreal Tournament 2004, the X3 series... etc., etc., etc.
Unless Mantle is a shedload easier to work with than OpenGL 3.x, I don't see it speeding the development of the Linux Unreal Engine 4 port. ;)
Bioshock Infinite? Starcraft 2? GTA V? Diablo 3? Skyrim? (I'm talking about native ports, not Wine)
Some of those you mentioned are Valve games, and they've been porting the games to Linux because of SteamOS.
I'm still not convinced that Mantle will be a significant motivator for AAA game producers to port to Linux. After all, if an "easier" way to get your game out the door was all that it took, wouldn't we have seen a bunch of Unreal Engine games on Linux back in 2004?
Can you convince me that Mantle is a substantially better or easier way of doing graphics programming than modern OpenGL?
Not sure. I'm surprised myself that there aren't more OpenGL games. One possibility is that OpenGL is too bloated/complicated (which Mantle would fix), but I don't know enough about OpenGL to state that with certainty.
