I'm making a 2D game, which is currently using SDL and OpenGL for rendering. Should I go out of my way to make an option to use OpenGL or SDL for rendering?

I wouldn't. It would be a lot of effort and I doubt many people would bother to switch renderers for a 2D game.

My advice is that if you want to include lots of alpha blending and rotation in your game, go with OpenGL as SDL is slow at those two. Otherwise, you can use either.