There are two elements in your question: 1. Vulkan becoming "THE" cross-platform graphics API and 2. This leading to games being truly platform agnostic. For 1

There are two elements in your question: 1. Vulkan becoming "THE" cross-platform graphics API and 2. This leading to games being truly platform agnostic. For 1, we already have OpenGL which theoretically is the true cross-platform graphics API. Vulkan adds another option for when you want more low level control (i've heard - i think from some Nvidia presentation - that a better way to think of Vulkan is as a GPU abstraction API that you use to build your own graphics API). For many years already, anyone who cared about writing a cross platform renderer with a single API, at least on desktop systems, would use OpenGL. For 2, generally speaking game engines tend to be platform agnostic and they were platform since the days of PS2 and original XBox and while there used to be engines that only supported a single playtform at the time, over the years this became less and less common and instead the engines are designed with portability in mind - especially since the last 10 years or so all games tend to be ported to Windows, XBox360 (or One for the latest gen) and PS3 (or PS4 for the latest gen) and each of those systems has their own specific APIs. Note that to do 2, all engines had to also support multiple graphics APIs by introducing their own abstraction layer for the native graphics API. Also note that an engine being platform agnostic doesn't necessarily mean that a game using this engine will be platform agnostic (e.g. UE4 does support Linux but you do not see all UE4 games supporting Linux). So basically, 1 cannot lead to 2 because 2 was already a thing for a long time. Now i will make an assumption here that what you really wanted to ask is that if Vulkan would make it more likely for Windows games to also be ported to Linux and OS X. Personally i wouldn't expect this to be any more likely than it would be without Vulkan (that is, the only cross platform option would be OpenGL), mainly because of Direct3D which allows a developer to support both Windows and XBox, where as Vulkan (and OpenGL) only supports desktop systems. The extra systems that Vulkan and OpenGL enable (Linux and OS X) have a very tiny market share that may not be worth the effort (not only in terms of programmer time). So i expect the situation to be exactly the same as with OpenGL: used mainly by those who focus on desktop systems and by those who use middleware and do not have much of a cost overhead to support Linux and OS X. And by those who prefer it for philosophical reasons, of course.