I threw out my guesses a while earlier, but if Canon were to build lenses specifically for me....
14-24 f/2.8 L
A new 100-400 f/4-5.6 IS L with the latest/greatest IS and an improved optical formula.
I'm really not hurting in the middle range, and their long lenses are already awesome. A little too expensive though, which is why I have the previous versions of two of them (but hey, a strong used market frees up cash for people to buy in the new market so there).
I'd love to have the 200-400 f/4 +1.4X but that's just out of my price range for now. Ditto on the 500/4 IS II, which is considerably lighter than my 400/2.8 IS. Either would be great for birding without the burden.