It's not just about a more comfortable ride.
There's a reason leaf spring suspension is still around. The method of creating a spring using a shallow U shape with a few strips of metal is older than the motor vehicle itself. Its simplicity and ruggedness ensures its longevity and when anything finally needs replacing then it's inexpensive and relatively simple to fix. There are also big benefits for trucks, like load distribution and strength for towing, but on the downside is a lack of ride comfort and compromised on-road performance. We don't expect the F-150 to ditch its leaf springs anytime soon, but MSN is reporting on spy photos showing a prototype 2021 F-150 Raptor out and about with coil springs on the back.
We say there are coil springs, but that's actually an assumption, albeit a safe one as you can't see the rear leaf springs that should be there due the heavy cladding added by Ford to hide as much of the suspension as possible. However, what we can see is hardware that suggests Ford is also testing a multi-link suspension setup. While the spring and multi-link setup testing could be a reaction to the RAM 1500's new setup and the 2021 Rebel TRX that's on its way, we're not so sure if Ford is planning a multi-link coil-sprung suspension for the Raptor.
The Raptor is designed more for fast off-roading, as in flying across dunes and down rough trails. The extra control a coil-sprung set up would give when tuning the suspension would be a night and day difference both on and off road. Add to that a multi-link setup, and tuning can minimize what's happening with one wheel on the back affecting the other wheel. That's not so important when off-roading larger obstacles or thick mud at low speed, but when corners start approaching at real speed then it can mean the difference between coming out sideways like a hero or ending up with bent bodywork in a ditch.