Will RouterOS x86 ever support Intel Wireless Cards?

Probably not, ROS uses custom drivers and all hardware is Atheros. Many features like NV2 probably depend on HW specific functions so I see it very unlikely to ever have intel wireless support. Even in Linux they seems to be more "high level" then Atheros, allowing less custom modulation settings etc.

As far as I understand, x86 is not actively developed anymore ... hence no new drivers. Hence no support for newer hardware. MT suggests to switch over to CHR ... for one thing MT down't have to develop tons of drivers, VM abstraction layer takes care of that.

With ROS7 things might change - who knows, MT might drop the "develop drivers in house" principle ... which would have nice side effect of allowing upgrades of kernel used in ROS without too much pain.