When I go for a Lifetime license, I’m investing more. Besides the larger investment, it also means I’m risking more. The plugin was great at that time but the future (specially with Gutenberg coming along) was uncertain.
They have to see me as a “stockholder”, a company “member”. I believed in what they were doing and invested in that. I “helped” to produce the product.
It would be very strange if they would ask me to pay again for something I own.
I don’t mind making a donation, if they have a method of doing so, and in my own free will.
The rest is up to the new methods of investment. If they have a good product, they can sell it well.