If you're going to use OpenGL, keep in mind that most PC games nowadays still support DirectX 9. This is the equivalent of OpenGL 2. Also, OpenGL driver support is generally lower than DirectX support (especially now that the XP issue is fading away). If you plan on releasing something soon, 2.1 may be the right version to target. The API is bigger, but as long as you shy away from the fixed function pipeline it won't be that much different from the new API.
Also you should be aware that SDL 2.0 is nearing release (for real). Unlike with OpenGL, you don't have to worry about somebody's machine not supporting new SDL, so you should grab the latest version and use that instead of the stable 1.2 release.