well the 2 biggest firms that have been really pushing for vulkan is AMD and Valve, Gabe newell made a statement at the launch of Vulkan :
"We are extremely pleased at the industry’s rapid execution on the Vulkan API initiative. Due to Vulkan’s cross platform availability, high performance and healthy open source ecosystem, we expect to see rapid uptake by software developers, far exceeding the adoption of similar APIs which are limited to specific operating systems"
and let's be honest most Devs are fed up with microsoft, and i am confident that they will pick up Vulkan, and it doesnt have to be as good as Mantle or DX12, but it needs to be decent quality and most importantly evolving at a higher rate than DX did in the past.
the last microsoft game did exactly what ppl feared, exclusif to Win10, and to top it all off, windows store exclusive, microsoft have no will to play nice or to commit to anything to PC gaming, Valve knows that, i just hope they continue with SteamOS and aggressivly push vulkan on steam