I came from a 550D and now have a 7D2 and a 5D3, so I don't directly know about the 7D and 5D2, except I'd say they are quite different. I think one of the things to think about is, what is it about your current camera that is not meeting your needs? For me it was frames per second and speed that prompted the upgrade.
The 7D is quicker, good for things like sports and wildlife. It has a cropped sensor. In a nutshell this means it gets you closer to the action for the same focal length lens. The downside (compared with the 5D2) is that it is not so good in low light at high ISO.
The 5D2 is a full frame camera. This means it has a bigger sensor, will be better in low light. It will require EF lenses, whereas the 7D will be able to use both EF and EF-S lenses. EF lenses are generally more expensive. I am not sure of the specs, but I expect it has far fewer focus points to choose from and less frames per second.
Your current lenses may not fit the 5D2 if they are EF-S lenses.
By the way I kept my 550D for a while as I was so attached to it, but in the end I just didn't use it, so I'd have been better off selling it as soon as I moved on.
If you're not certain what your needs are, then I'd wait to before deciding. Good luck with your choice.
