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.
