It's easy to get caught up with the latest, greatest, newest and want to upgrade (even if it will be second hand).
If you are happy with your equipment (and I see no reason not to be), I would look at working on the craft of photography: composition, perspective, exposure, flash, etc.
If you are going to upgrade, the look at where your holes are in your kit. (If you fill out your equipment profile, we can see what you are using and make recommendations). But before that, ask yourself this: What does the equipment NOT do that you want it to do?
Can you verbalize what you are looking for in your gear? Do you have a good, sturdy tripod? Do you shoot flash? Do you have a flash? Are you interested in multiple flash? What do you normally shoot? What are you happy with your lenses? Are they fast enough?