A French company should now be able to offer a chat messenger which is interoperable with Skype for sale, potentially giving it to keep up with the cat and mouse game.
Also, the ability to run chat bots on the Skype network is something that can be quite valuable for certain companies.
For others proprietary softwares, breaking the compatibility with old versions is hardly conceivable: If Photoshop or AutoCAD where suddenly unable to use read and write the terabytes of data created by their users, those users would probably throw their PC through the window and never buy again a proprietary software...