I agree with Ravyne above. As someone who probably moved into 3D too soon, I've found that, while in theory they're similar, some of the details and boilerplate things get extremely complicated rather quickly. In hindsight, I would probably have had a much smoother time in the learning process had I waited a bit longer, and likely wouldn't struggle nearly as much as I still do.(I had only been programming for a few months when I moved into opengl, probably much to everyone's dismay in the opengl forums).
That 3rd degree of movement gets tricky the moment you realize that Euler angles aren't going to suit your needs. Animation gets vastly more complicated than sprite-sheets ever could be. You have the addition of handling projection and view matrices (and matrix math in general). The boilerplate directx/opengl stuff is far more complicated than rendering sprites via SFML/SDL. You need to learn your shader language and more importantly, how to render proper lighting, normal mapping, shadows, etc.
With that extra overhead, you're now needing to consider performance (perhaps really for the first time), and streamlining your rendering operations.
In addition to that, if you're developing on your own, you'll need to learn to 3D model, texture, and animate, which I'd say is close to on par with the timeline to learn the programming side of things, if you want things looking even semi-decent. And while we're talking about time, the modeling side of things take so, so long.
Anyhow, I'd just say to make sure you have a solid grasp on things in the 2D world, and be prepared for learning and development of a game to go much more slowly when you add that extra dimension.
Edit*
To be clear, I'm not trying to talk anyone out of learning something new or to even necessarily discourage moving into 3D. I just wanted to give the perspective of someone who did move to 3D rather early on in their learning curve, and note some of the pitfalls and likely struggles ahead. If you're totally comfortable with creating 2D games, and the concepts involved, then I think by all means, forge ahead :)