Mozilla are working on a "Wayland DMABuf" feature which will allow for separate processes to share GPU buffers on Linux[1]. For a long time that has been a blocker for hardware-accelerated video decoding as otherwise the data would need to be copied GPU->CPU->GPU which would negate a large portion of the gains. In the short term the work will only apply to WebGL rendering but it should open the door to hardware-accelerated video decoding in the near future.
[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1572697