Now with some smartphones having 6 inch screens, they now compete with some tablets - are they actually smaller tablets, or still smartphones? CNET has an article describing the large screens on the market. I have a Nexus 4 and iPhone 5, they are just the right size I don't have to worry about putting one in a special case - it could look like a small envelope being carried around, or being very cumbersome on a belt holster!
It will be interesting to see what the limit, if any the consumer will tolerate. Be it that many people carry their smartphones with them in plain view while walking down the street (hello stolen phone thiefs!), probably because I lived a long time before phones/smartphones engorged the masses - so I can walk down the street or be at a shop and not always being glued to my smartphone - though I do use my iPhone notes app for writing down my grocery list, saves from using a post-it note that I usually forget to bring with me.