Game developers can now pre-order Unity 5, which includes high-end shader improvements, audio improvements, a 64-bit Unity Editor, WebGL export support, mobile improvements, real-time global illumination, PhysX 3.3 support, 2D enhancements, and a whole lot of other features.
Unity 5 overall looks very exciting and continues to bake in Linux support. Unfortunately, it still doesn't look like the Unity Editor will be coming natively to Linux.
Those wishing to find out more about Unity 5 and aren't present at GDC can visit Unity3D.com. I'll be out at GDC on Thursday and Friday with Linux gaming coverage on Phoronix so stay tuned for more.