Of course the APIs and drivers will improve, thats the same for any hardware, but no there is no such thing as secret sauce. The hardware is what it is.
@xenostar @vivster api's and drivers are going to improve but if you bing it or google it you can see a decent amount of difference between directx 11 and 10 amd mantle improved the perfomance by huge means 30-35% so directx can. Their are many things ms has to answer about.
Mantle brought performance boost to PC because with it AMD emulated console like low level access API. We have had those with consoles since dawn of consoles. That is why you have usually gotten a lot prettier game out of console than from PC with same specs because with console you could code on ''metal''. You don't get same level of performance boost with any API on consoles simply because with consoles you already have low level access API. Of course drivers and APIs improve during the console cycle but they are not ''secret sauce''.
Edit. Damn. Hinch pretty much said the same just post above me.