Intel's drivers seem to work under Linux pretty much as well as they do under Windows, so they at least can manage to achieve acceptable results even without any special technique that supposedly they woudln't want to use in the open. I hope that in the future, either their upcoming hardware or AMD's open source drivers will raise the bar for open source graphics stacks, as Linux did for open source operating systems. Then Nvidia will feel it more "natural" to join the others.
No announcement yet.
There's Hope For DMA-BUF With Non-GPL Drivers