As for waiting, why?
There are two reasons for me:
The 5D3 has a pretty high level of fixed pattern noise at high ISO. The 7DII seems to solve this. I'd like to see them solve it on full-frame too since fixed-pattern noise is really hard to remove, and pretty distracting to me.
I want to use this camera for video as well as stills and the dual-pixel focusing system on the 70D and 7DII are pretty game-changing in that area. Again, I'd like a full-frame version of the same technology.
Since Canon obviously has the technology to solve both "problems" (since both are solved on the 7DII) I'm looking forward to the 6D and 5DIII replacements before I purchase a new full-frame camera.