I disagree on this with regard to no obligations because it is free, before Adobe went all-in on subscription people were notified that they had to upgrade to the latest CS versions to be able to update yearly. Shortly after the deadline they announced there would be no future perpetual CS version, only subscription. Adobe just dropped the entire CS perpetual license despite lots of people having just paid quite a bit to be upgraded to the latest perpetual CS version.

Being a paying customer does not bring future obligations to their customers.

If a company thinks it is better to drop their existing products for something entirely new with a new file format etc. they can do so as they please Or just drop segments of their products with no new alternatives.
I have experienced that more than once with a company collapsing, or just quitting.
Adobe killed FreeHand, GoLive Cyberstudio, PageMaker (though InDesign was a good replacement) for products that I considered to be lesser. FreeHand ran circles around Illustrator at the time for example.

FOSS may be good for professional use in some cases, not really suitable for heavy professional use in more cases but you are dependent on volunteers. Unless they are well funded like Blender, LibreOffice, Open Design Alliance (ODA) and QGIS to name a few by users who have a significant stake for the software to remain actively developed. Or you have to deal with very small businesses (1-3 people) and hope there will be someone in the future to keep it going when the founder retires (e.g. PhotoLine, VectorStyler, High-Logic FontCreator and MainType).

There is no guarantee for any software to last indefinitely for anyone unless they develop it themselves (of pay others for the continuous development on your behalf). All we can hope for is that the file formats will be somewhat neutral so that they can easily be opened in other software should your preferred software cease to exist/being further developed. (e.g. OpenOffice formats, SVG, DWG etc.)