The latest rumors are that it's not 'emerging markets' but rather China Mobile specifically. They use, it seems, a very unique form of CDMA that everyone else dropped support for ages ago (sort of like the whole thing with T-mobile in the US). So Apple would have to make a phone just for them and this is that phone. Opening up something like half a billion potential sales.
There is no way Apple is going to limit the iPhone 5C to just China or emerging markets. This phone will go on sale worldwide from day one.