Not a direct photoshop replacement, but for specific photo editing of RAW photos, have you tried darktable? (http://www.darktable.org/)

It's not as good as Lightroom, but I'd say it's 80% of the way there, and you can replicate some of the missing functionality with other applications.

The latest Photoshop on Linux is quite attainable; I have CC running smoothly via VMWare Worksation 12 / Windows 7 (new versions of VMWare have DirectX/OpenGL and let you allocate GPU memory)

... but unfortunately that combines 2 proprietary solutions so guess it doesn't exactly fit your criteria.

So "Photoshop on Linux" means "Photoshop on Windows on Linux"... that's not really a solution. That's Windows.

Heh, good point at least though with this setup you don't have to boot into it or use it for anything else.

I've been using RawTherapee for a few months. It doesn't rival Photoshop, but it is useful.

Photoshop runs pretty well on virtualbox last time I tried it (~6 months ago). That was for very very basic projects though, not sure how it behaves in big ones

Or simply a linux port of the creative suite?

Yeah, simply.