Ugh... At the risk of sounding like a guy who thinks he knows things...
Kontakt is NOT the future.
Innovation disrupts, not following standards. (StaffPad, Infinite Brass, etc.)
VSL has endless features. Stable, but right? No way. Just agile. Hardly the future of sampling.
You should never have to look at a sampler, so a central uniform tool isn't the issue.
UX = Software is like a joke. If you have to explain it, it's not that good.
I read manuals. I like to make use of what I have. But I once designed a DAW/Notation hybrid, fleshed out features, and wasted time being an idealist... every time I got to the sampler, I realized more and more that the ideal UX is to simply not have a sampler GUI at all. Everyone SAYS they want simple, open, free, universal, and stable. Awesome, maybe it can make breakfast too. Simplicity has far more value though.
I care less about GUI and standards and branding in every corner and more about whether the product is any good. If Spitfire sounded as good as Spitfire and as agile as Infinite Brass and it only ran in FL Studio, I'd buy FL Studio today. The sampler isn't nearly as important as workflow. I'm not ranting about Spitfire's agility either. I'm saying that which platforms are used is not nearly as important as whether they are used well.
Open is great for UX and I either do things open or I make it open by ripping it apart. I value having control over my tools. Call me obsessive. But that still matters less than having something work right. I can't control StaffPad. I can't put my sounds in it (wish I could), but I still use StaffPad more than Dorico and S1 more than Cubase. I like all of them in different ways. But the future? The thing companies OUGHT to do?
The platform really isn't the important thing. It's doing what you do as well as you can.