Seems to me that a bigger problem, at least for ARM SoCs, is that the SoC vendors are only developing binary drivers for Android's kernel+framebuffer. X11 and A

Seems to me that a bigger problem, at least for ARM SoCs, is that the SoC vendors are only developing binary drivers for Android's kernel+framebuffer. X11 and Android have a rather different model for GPU drivers, and you can't just port a binary driver from one to the other.