I took a Canon 7D and 2 lenses to Namibia last summer. A Canon 100-400 and Canon 17-55 f2.8. For me, this was a perfect combination. If you wanted a upgrade in lens, you could go with a Tamron G2 70-200 f2.8 (which I have, great lens) but would likely need at least a 1.4x teleconverter, making a functional f4 lens. I used the 17-55 around camp and for low light and landscape stuff, the 100-400 was used for nearly all the wildlife stuff.
[Linked Image from photos.smugmug.com]
[Linked Image from photos.smugmug.com]