Making games for only one platform doesn't make sense since it limits reach, and using tons of incompatible APIs is annoying as well. Vulkan is low enough of an abstraction to perform quite well, so no matter what direction something can be ported, having a common API can save a lot of time.

Here is what some say about it: http://gamingbolt.com/ps4-should-support-vulkan-ps4s-api-not...