There was some traffic on the mesa mailing list in the last couple of months about alternative GBM back-ends, which is basically about nVidia partially conceeding they aren't going to win the GBM vs. EGL Streams discussion and tweaking things on their side to reduce the differences, combined with compromise on the mesa side to allow alternatives to current libgbm; which isn't so objectionable now the EGL Streams "GBM" shim makes the differences relatively minor.
This basically allows Tegra DRM drivers to plug into mesa's userspace rendering infra which is well proven and widely supported; the shift from X11 is gathering momentum and Wayland needs mesa. Tegra V4L2 accelerated decoding is then the (non-trivial) missing link. If V4L2 compliant DRM/ffmpeg drivers are written (compliant to kernel V4L2, not some proprietary nVidia-ised interpretation) Kodi should require no changes to support Tegra boards. That's the theory anyway