If you need years to transition off Flash you should have started years ago and if you haven't yet, you have a very big problem on your hands. And if you think Adobe cares about that you are mistaken. They don't care unless they can make money out of it. They are not a charity.
I'm currently involved with a business transitioning their content from Flash to HTML5 and they are adamant about completely removing any Adobe software from the stack.
This means that they won't be using the HTML5 backend of Adobe Animate (formerly Adobe Flash Pro) out of principle, even though in this case it would be acceptable to keep it around as an authoring tool.
By the way, the same is true for any Google software, they won't be using (for instance) Google Web Designer because of Google's extremely poor track record of supporting software in the long run.
Another thing I'd be curious about is the line at which the opportunity cost of not making the transition surpasses the cost of not developing new Flash features.
When a bank CEO, who has no idea about anything except "Well Adobe is a big company and I've never heard anything about this W3C, and how long will it take? How much will I make off it right now?" hears (if he even does) that Apple doesn't like flash, he won't care.
We are currently shoring up this old app while simultaneously building a new, modern in from scratch.
It is a constant battle of bug fixes on the old and implementation and new features in both platforms as we try to transition customers off.
I do wish the actionscript and flex ecosystems were still thriving because we could use the help. I imagine other enterprises are in the same place.
In the early 2000's I worked for an e-learning company. All of their courses were interactive, popular with large corporations and trained employees from fire safety, to compliance to business processes. It had user testing built in and in order to deliver the interactivity and keep it interesting, Flash was the perfect tool. It has great hooks that you could use JavaScript to get data and out, and interface with backbend databases/scripts and of the shelf e-learning management systems.
Much of those e-learning courses are still being used today. Most of the content is still relevant today. It makes no sense to throw it away.
It is companies like these and those of the parent poster, that are the key reason why Adobe cannot simply pull the kill switch
The real story for Java and Flash is not having to worry about browser compatibility something I think many think has gone away with webkit but the reality is it is still here and worse than ever (mobile, firefox, ms edge).
Someone always signals there will be a price to pay. The thing is, the price is not high enough when compared to the profit you gain by continuing down the road you are on now.