Maybe this means Canonical will focus more on ARM hardware now, which is kind of the point of Mir anyway - to be a lot more efficient on "lower-end" mobile hardware like ARM chips. Can't say I wouldn't like that to happen.
True enough. No support for NVIDIA cards at all in current Ubuntu betas. I think even nouveau was falling back to X compatibility but I might have that wrong. It was sloooow
It would be smart to focus on ARM as a long-term strategy. There is a huge investment and legacy in x86 but if history is right, ARM will eat up x86 from the bottom-up just like x86 did to the other ISA's.
Of course the ARM future is not all that glorious. The open-source friendly ARM vendors are not that common, most ARM GPUs do not have (1st party) opensource graphics drivers.