Apple is about to introduce an 8gb 5c at a cheaper cost. This shows that the 16gb is going to stay for a while longer as the base model.
http://www.engadget.com/2014/03/17/apple-could-launch-8gb-iphone-5c-rumor/
http://www.engadget.com/2014/03/17/apple-could-launch-8gb-iphone-5c-rumor/