Re: GIMP is, or at least has been enough of a match for most of what PhotoShop did
There's nothing to keep Adobe, Autodesk and the rest on Windows but their customers. They just follow the money. And increasingly, the only argument for staying on windows is that you have applications that need it.
This is an unstable situation. In many markets, the leaders have already moved to Linux (engineering) or Apple ("creatives"). It's only the risk-averse and the don't-cares that are left behind. Once the tipping point comes, they'll follow the herd, just like they always do.