I have to wonder just how much is generated for Adobe via CC now that they also have that marketing service, that's really all about data mining as well. It still may pale in comparison, but I do have to wonder.
I would argue that Adobe's rule now is more about perception than anything for a lot of people. Sure, for some there are some workflows that really do still depend on Adobe, but I would say that that is still a smaller niche group compared to all those that subscribe to Adobe. People believe that they have to have X when in quite a lot of times, it's technically not the case as much as they would think that it is. Especially if one is not really needing to accept outside files (I would say that's the single biggest reason why people "need" Adobe, the other is that they are more or less familiar with the Adobe workflow and don't really want to change (I'm guilty of this as well depending on the software)). Features, while some features may not be available in the open source variant, some features do (even ones that some didn't originally think that they do), and while they may be implemented differently (for one reason or another) they do still exist. Now if one wants to debate UX about how those features are implemented that's something else. Just think of how many people have that perception of using Adobe or bust? Shoot there are some on here that it is either Mac or bust as well. And I think just in general people think open source is lacking in quality (and for some, that is the case and that also applies to lack in quality for pay programs as well, even ones that were once good).
Also given the age of Adobe suite of programs, there is a lot of technical debt that does not exist in younger programs (same thing with Corel as well and they have their own issues from what I have been hearing).
Times change, what really worked when people learned things whatever time period may not exactly hold true today. Change with the times or the times change you.
As to open source pantone colors, yes there are such things. Typically they are in the .gpl format (no not the license) and most open source programs can use those as swatches. Depending on what one is converting over and what resources that are available determines how much of an effort that it is. But yes, efforts along those lines have been going on, for a long time actually. I have had pantone swatches in Inkscape since 2015. The oldest version of this swatch came from 2011 or 2012, can't remember. Although, I actually use Blender for 2D vector graphics now (not something that I would suggest for everyone though, but it does work and I like it better compared to Inkscape).
As to what will happen with Adobe programs after Pantone is culled from there. I look to how they handled the Dolby issue. It is far easier for those on SaaS to control things. Easily force people on to versions that don't support Pantone, in an update, look for those pantone swatch files and remove them periodically (gotta love perpetually connected programs) for those that still may be using those older program versions. And I would say that the checking and removing would probably be more than just once, probably have some regular check in as well. Those are just two things that pop right into my mind. It could also be probable to eliminate just how easy it is for those older program versions (that are CC and still supported at this time) can read those files even if one did re-import them with an update. I'm sure that there exist easier methods compared to what I'm thinking about depending on how everything is handled.