Never going to happen. The last time Shimano invented a new freehub standard Sram didn't even make hubs. Yet they still came along and took a massive portion of the oem market. Shimano needs their microspline groups to be a big oem success and they're definitely not going to help sram fight them
Truth. Sram will not (ever) sell you a microspline freehub for their hubs.
However, I wouldn't be surprised if Sram 900 hubs are "produced/sourced" generically and branded differently for various OEM's. One of which might also produce a microspline freehub body.
Said differently: I wouldn't be surprised if the factory in Asia that manufactures Sram 900 hub shells also manufactures a microspline freehub that would work just fine. That said, identifying which microspline hub to get for it would be tough. We need someone who knows the supply chains!