walt-m and mipevo6 are absolutely spot on. If you're considering a 7d it sounds like your budget is around a grand. The glass you can get for that money will be a miles better investment than buying a new camera. It depends what type of wildlife you fancy shooting, if you can get reasonably close a 70-200mm f2.8 non is is the one, if you need more reach the 100-400mm L will do. If you're after the smaller stuff, get the 200mm f2.8L and a 60 or 100mm macro.
The 40d is a good camera and married with these lenses will be capable of cracking results