I recently bought a 2014 F150 Scab XLT with 3.5 liter turbo. I love it, light years ahead of my older 5.4 triton. What makes my 2014 different from a 2015, the aluminum body? Will parts from a 2015 fit the '14? I ask as the 'new' series (generation?) begins with 2015's. What makes for a generation? what generation is the 2014? I've found opinions, but is there a definite answer?

 

A generation is when a new design comes out. And depending on the manufacturers following the name could be something like 1G, 1GB, 2G, 2GB with the B meaning it is the same model but with some slight variances like grill, bumpers (usually cosmetic things but could be an updated powertrani like the trans or more hp/tq).
So yes, the 15 & 16 are the newest generation. I'm not sure what years the previous gen extended to.

As far as parts - almost always major parts don't swap but there are always exceptions.

 

Your generation would be 12 gen (09-14). Even then there are some change in parts between the years for instance your IFS is a bit different from 09-13. Best not to assume and just ask for each specific case.

 

Read up on the new 3.5 which has alot of the features of the 2.7, with even greater torque of the previous 3.5 and better fuel mileage according to Ford. 10 speed trans will likely play a big role in this. But then people need to decide if they want to be the tester of the new 10 speed for a year.