Very neat, very simple idea and very well executed. Bravo Mercedes, Bravo!
I think the above video explanation is wrong, the geometry movements of a sliding steering rack by the small distance shown by the wheel movement wouldn't create enough toe adjustment. Without looking at the rules with regards to legality I'd put my money on it to be more a hydraulic system than mechanical system
I'm sure the main purpose of the system is to improve aero performance by reducing the front tyre wake which in turn reduces drag. Basically a front tyre DRS, the aero development program will be entirely based around it. Any benefits with evening out the tyre temp/reducing tyre degradation before cornering would be a secondary benefit.
I'd be very surprised if another team copies this before the end of the season, it would require major changes/new chassis that would require re-taking the front crash test. On top of that the drivers would require endless hours of simulator driving. Also design department's will be too pre-occupied with the 2021 car rule changes and 2020 aero updates for the amount of distraction it would cause for a end of season running before it's banned for 2021
I have heard Mercedes had this system in development for 2 years and after repeated clarification's from the FIA they end up with a slightly watered down 'legal' version. If true I doubt any other team could copy it in 6 months