Not long now on the Krita kickstarter.
In case you don't know what Krita is its a paint package. Similar to Painter, so very brush focused. Where as Photoshop was more about photo work originally.
It was KDE only and even then quite niche. It's now opened up and there is Windows port.
Take a look, and see if its your thing.
They look to be branching out into animation and also Photoshop compatibility. So bare in mind its potential.