There will be, however, still people who want to use Windows in order to have access to their programs that cannot be found in Linux (Photoshop, Corel PaintShop Pro etc.).
So they could not use GIMP then? It's free.
To be honest, 99% of users don't need Adobe Photoshop or equivalent at all, perfectly adequate editing available in even phones these days for most uses.
Almost all home users use Windows out of ignorance, fear or lethargy rather than need. (This does not mean you dear reader)
Windows is only used for games because of critical mass, once that is eroded it will fall away rapidly.
The original iPad, and the tablets that followed have kick started this sea change in home computing where John and Jane Doe realise they really don't need a PC. If you are reading this forum you are probably not one of them but people often have trouble in realising the landscape of home users and assume they conform in some way to their own perspectives. It's hard to so, this was the 'genius' of Steve Jobs in that he saw beyond that and was able push out the frontier ( not Frontier ;-) )
I am very interested in what Frontier are doing with Cobra, from what I understand it is a powerful abstraction layer that means they can easily port to any platform they wish. To perform it must be immensely powerful and ED is probably going to be a showcase for what must be the company's most valuable asset.
I don't see any technical, non-licensing reason why ED would be eventually ported to Steam.