Ford already sells compressed natural gas (CNG) Super Duties in a collaboration with Westport systems, but if pickuptrucks.com is to be believed, they might be rolling out a CNG F-150 themselves soon.
Admittedly, the grounds for this assertion are pretty shaky (the have a pictures an F-150 with a CNG sticker on it), but it’s not a far fetched idea. Only Ford could build a CNG truck that retains the factory backed warranty. Currently the other conversions on the market will void your warranty. That makes them great for people with older trucks, but it increases the costs of having a new CNG truck significantly.
The draw of CNG (and to an extent, LPG) is easy to understand. In most places, CNG is inexpensive when compared to gasoline. The downside is that the tanks tend to take up a lot of space in the bed of the truck. It tends to make less power and be less efficient. But it is cheap and clean.