It's almost hard to believe how far Linux gaming has come just in the past, what, two years?
I think it really started with the Humble Indie Bundle's mandatory Linux support, accelerated with the help of Unity and Kickstarter, and really achieved mainstream legitimacy with Steam. As long as the GPU manufacturers cooperate and write good drivers, the future looks very bright indeed.
I think worldwide support/adaption of the Steam Machines will basically make it so GPU manufacturers have really no choice but to write amazing Linux drivers. If they don't then they'll more than likely be chosen less by companies producing (yearly?) Steam Machines.
Unless they only write good custom drivers for hardware they know will be used in Steam machines. Don't know of any reason why they'd do that, though... I'm hopeful :)
Finally. The year of the Linux desktop is upon us!
For now. One of the developers mentioned on Reddit that editor support is planned for the future.
Plus, unlike Unity, you could theoretically port it yourself. Paying $20/month gives you complete access to the source on GitHub, and they're going to start accepting pull requests very soon.
They already are accepting pull requests - several have appeared in hotfixes. There's a link to some of the pull requests in that blog post, although I'm not certain you can access them unless you've paid the subscription and setup your github account link. There are a few really quite cool pull requests being reviewed just now too.
The github repo contains the entire engine and editor source. The only thing not included there is closed console support, which you have to ask for just to ensure NDAs are in place. So, yes, you could in fact port it over to Linux.
It depends on your level of programming expertise and how deep you want to get into the discipline, and what sort of games you want to make.
If you want to make 3d games for major platforms and are of moderate to high programming talent, it's hard to beat Unity at this time. The Unity Asset Store is an inexpensive source of great starter projects, temp assets, and commonly needed libraries.
That said, making 3d games at all is deeply nontrivial and I wouldn't recommend it as a solo hobby owing to the very large surface area (art, design, game design, geometry, game logic, tooling, etc.). You can get to the 85% level in everything but modern consumers will be unsatisfied with the quality.
For 2D, especially for getting to a shippable product, I might try LOVE or Moai, although both of those are on shakier foundations support-wise. Don't let anyone tell you having anything to do with Python.
