x86 cRIOs have existed since at least 2011, if I recall correctly. As for the roboRIO 2, FIRST has already given an official statement on the next control system in this blog post:
We received cooperative proposals from National Instruments and REV Robotics that complement FIRST’s technical needs and mission, and we’re happy to announce that the 2022-2026 system will consist of a revised roboRIO from National Instruments (increased RAM and flash memory, improved low-voltage protection, and a higher-speed grade Zynq processor) and support boards being developed by REV Robotics.
All the Zynq boards are ARM-based as far as I can tell.
Actually, teams have been able to run their robot code on personal laptops since 2019. WPILib natively targets Windows 32 and 64-bit, Linux x86, Linux ARM (roboRIO and Raspberry Pi), and macOS. Local unit testing is also supported (here’s my team’s tests, for example). I guess we’ve historically been bad at advertising our existing features.
Given the current state of the world, we’re prioritizing a simulation frontend for 2021 as well as high-fidelity physics simulation using the recently merged model-based control libraries as a backend. It’ll support drivetrain, elevator, single-jointed arm, and flywheel mechanism simulation. The gist is in
simulationPeriodic(), you give a mechanism simulation object motor voltages, run an update() function with a simulation timestep, then set the encoder values using that object’s position getters. One of the primary design goals was not having to touch existing teleop or autonomous code to facilitate a physics backend.