From John's previous post on this topic: [Let's assume that doesn't happen & think creatively about other approaches. --J.]
The lack of practical alternatives to the key Adobe apps has allowed Adobe take control of the customer relationship by attempting to enforce a subscription-only scheme.
It's time for some small, nimble and innovative software companies to step in and challenge the Adobe monopoly, in the same way that Adobe stepped in and challenged the existing publishing/typesetting monopoly in the 1980s.
One of the fledgling alternative image editor companies that has already proven their capabilities could start a crowd-funding project called "Let's build a good enough Photoshop alternative".
Of course they cannot expect to replicate all of Photoshop, but if they could attract some really smart programmers and designers to their team, they could set a goal of creating a "good enough" replacement for Photoshop in, say, two years.
The deal would be that they would promise to offer saving/exporting to publicly documented file formats, sell it at a fair price (a smaller operation would have much lower overheads than corporate Adobe) and NOT adopt a rental model.
I get the sense there are people ready to jump from the Adobe ship if there was a "good enough" alternative.
I would certainly make a donation as an insurance policy for the day when I might need a Photoshop exit option.
The same could be done for a vector illustration tool.
(Or perhaps one tool could do both. There are already examples of software which bridges the two paradigms, and Photoshop and Illustrator have been progressively encroaching on each other's territory anyway.)
Some Adobe apps already have viable alternatives: Premiere Pro (video editing), Audition (audio editing), Dreamweaver (web design), After Effects (video effects), etc.
The difficult one would be InDesign. There's a lot of arcane knowledge built into InDesign.
History tells us that monopolies are seldom a good thing.
Practical alternatives, i.e. real competition, is really the only long term solution. It would shift the power back into the customer's hands.