Not a fan of the "one lens is liberating" school of thought.
At the same time, I'm not a fan of the "I own it, so I brought it" school of thought.
If I were going on a trip in which photography were going to be a major element (i.e., more than just snapshots), there is no way I'd take only one body/lens. It would be two bodies and 2-3 lenses. 
One wide, one normal and one telephoto. The only reason I'd bring the normal lens is to back up the wide and the telephoto. It's not a perfect backup, but it can do a little of what they do.