Personally I don't care about natural wonders much, I think they should give a happyness bonus only if they are in your territory. And I hope they put map trading back in one of the next patches.
And given that a single resource gives as much happiness as 5 natural wonders, there's no reason not to have more of said natural wonders. Perhaps all in the expansion...
Ahhh nooo please don't say something like this when we know they're planning to go for some cheap one or two civ DLC packs...
"Civilization V: Wonders of the World, episode 1. Discover the amazing mountain scenery of Southern Switzerland with four new wonders of the world that each add one happiness to your empire. Stay tuned for episode 2 due for an early Christmas release, where you will explore Northern Switzerland and Lake Constance!"