If Apple is developing a fanless MacBook, it presents some interesting possibilities.

Will Apple bring out a newfangled, 12-inch MacBook? Only Apple knows, of course, but let's look at some possibilities if it does.
We'll start with the supply-chain-sourced speculation. Several sources, including NPD DisplaySearch and KGI Securities analyst Ming-Chi Kuo, are anticipating -- and have been for some time -- a 12-inch MacBook.
It's not clear whether it would be a new MacBook Air or an entirely different concept, though it should be noted that most informed, Asia-based speculation to date does not always make a direct reference to the Air.
The latest speculation is the most interesting because it refers to a fanless design. That could imply several things.
--Hybrid: Typically, the reason a device maker goes with a fanless design is to put the electronics behind the glass -- not under the keyboard, like typical laptops. Behind-the-glass usually implies a tablet or a hybrid -- the latter along the lines of the Surface Pro 2 or Dell Venue 11 Pro. And note that though it's a hybrid, the Venue 11 Pro can be described (and indeed looks like) a traditional clamshell when the keyboard is attached.