We see that already with CMSes and CRMs. Sure Wordpress is a beast, but the vast majority of that complexity comes from it being universal.
I've seen non-technical people building their CMSes and even CRMs for small businesses within a fraction of time it would take them to set up the off the shelf product. The biggest challenge there is security of course - but Photoshop clones don't have to deal with it too much.
My bet is that in single months we will have a stable clone of the Photoshop core, and with an ability to easily modify it, designers will just build their own custom plugins to fit their workflows better than PS ever could.
Unlike CMS/CRMs the cost of switch/testing out is minimal. You don't need to switch the whole company to it, you don't have security issues, and if it's too buggy you just switch back.
Also, this is a way for graphic designers to maintain their relevance - if they can have full controls of their tools, they can do the work faster and better and maintain their creative freedom.