The flaw with this reasoning is that Eagle is not currently a class-leading tool. Its niche has been the maker/small business space, and its customers have neither the need nor the financial means to afford a best-in-class tool.
I think this is the key problem. I've not used Eagle but my understanding is its main attractive feature is being free, and people only buy the non-free version because it's what they know.
So where 's the ongoing future market ?
Anyone starting out from scratch (or deciding how to transition form Free Eagle) is probably going to take a very hard look at Kicad and alternatives like Designspark, Diptrace etc. I've not used Kicad but seeing what people have done with it, it must be pretty useable and it can only get better.
Many existing paying Eagle users will probably subscribe.
Unless they do some very major improvements to make it much more attractive to new users than Kicad, I think they have a rather stagnant and diminishing user base.
Question for people who have used a reasonable number of PCB packages - given a choice based purely on UI and features, not price, how many would choose Eagle?
Given what they must have paid for Eagle, I wonder if they could have got more value by writing something completely new with world-beating features, rather than inheriting a lot of legacy baggage.
Comparisons have been made to Fusion360, but from what I've seen this is a class-leading tool which offers way more for the money than anything else on the market - as & when I have a need for serious 3D design I wouldn't hesitate to subscribe.