He's just saying that because Khronos has actually done that exact thing before...
It is very unlikely. Vulkan and OpenGL are two different paths. They will continue to coexist for many years to come.
They were supposed to ve working on a new, modern, clean API called Longs Peak, which would break backwards compatibility with GL. And , after setting the hype train in motion, they released a new GL instead (and handed API war victory to D3D on a silver platter).
If they did the same thing this time, my bet would be on Valve taking to initiative to finish Mantle/Vulakn/Valven on their own, and form a new comittee making Khronos redundant. So, failure is not an option for them this time.
Well, the story about Longs Peak is a bit different. That was a threat to cease support for legacy OpenGL in the upcoming drivers. That's why OpenGL 3.0 didn't break backward compatibility. This time, Vulkan will coexist with OpenGL. Furthermore, OpenGL will be a more popular API for many years to come, because of the higher level of abstraction, the easiness of the usage and less responsibility for the programmers. Many of them are not aware of what the drivers do for them. Vulkan would change it a lot. Also, Vulkan is both graphics and computation API. Valve is deeply involved, but the support of big players and hardware vendors is even more important. NVIDIA already has support for Vulkan in its drivers.