Eurogamer spoke with 4A's CTO, Oles Shishkovstov, and Linux/SteamOS was brought up. In regards to Linux/SteamOS with OpenGL, Oles responded, "Yes, the original Metro Last Light Linux port was based on OpenGL 3.2 - it was stable but did not support high-end features. For Redux we are essentially replicating the DX11 version, with almost one-to-one correspondence in features. The downside of that approach - the GPU should be at least OpenGL 4 'core profile'."
Hitting parity with the DirectX 11 version of Metro Redux is fantstic for ensuring a quality Linux port, but mandates OpenGL 4.x requirements. This is no problem if you're running a modern Radeon or GeForce graphics card where the proprietary NVIDIA and AMD Catalyst Linux graphics drivers expose OpenGL 4.4 (or even OpenGL 4.5 with the new NVIDIA driver). Realistically, you probably will be best off with the proprietary NVIDIA Linux driver at least initially... I'd be incredibly surprised if the mainline AMD Catalyst driver at the time of the game's release can fully run Metro Redux without any rendering, stability, or performance issues. Catalyst has been making progress for Linux gaming but it's frequently recommended by Linux game developers to use the NVIDIA driver for a trouble-free experience.
The Intel, Radeon, and Nouveau drivers in Mesa meanwhile expose OpenGL 3.3 compliance with various extensions of GL4 currently being implemented but not enough to claim OpenGL 4.0 compliance. Mesa is nearing OpenGL 4.0 support and will hopefully hit it by the end of 2014 for at least the Intel DRI driver but also hopefully Gallium3D's R600/RadeonSI and Nouveau NV50/NVC0 will be in working shape.
There isn't yet a definitive date for the Linux release of Metro Redux but based upon recent SteamDB it's looking to come soon... For now you'll either need to be a user of the proprietary NVIDIA/AMD Linux graphics drivers or hold out a few months for improved Mesa GL support and hope that the open-source graphics drivers offer fast enough performance to make a playable experience.
When Metro Redux is out hopefully it will be benchmark-friendly so we can deliver a swarm of new Linux gaming performance tests at Phoronix.