Yes, namespacing is the best currently available option. Unfortunately its only an approximation of lexical scope, as the example in the presentation shows (the one with the two red buttons).

True, this is not something that happens often, and we can mostly get away with namespaces. But that's not the point. The point is that lexical scope is a tried and proven (by years of research, in multiple languages) solution to this problem which doesn't have any of these quirks. And JS has lexical scope.