This is a terrible mistake. People see Prusa as a premium brand mainly because of its long history in open source. You can buy a similar Creality printer for like $200 from Amazon vs Prusa's $800 or whatever shipped from Europe already.

Barring any overwhelming breakthrough, other brands have them beat on price and performance. Hopefully they at least keep middle of the road models as open-source for those who really value that. I anticipate that the open-source printers will outsell the closed-source ones, unless they conceal the fact that they are now closed source.

By the way Prusa, if you don't want to help the competition, maybe don't let Prusa Slicer slice for other printers. But that cat is out of the bag, and it's also probably a marketing tool at this point.