What is there to advise? It is a known issue that effects some, not all, and is fixable. If it happens, you can get it fixed, live with it or get rid of the truck. What are you afraid of exactly?
You just have to decide your level of comfort. Ford says the cam phaser issue will not damage the engine if you don't fix it, yet they extend the coverage for it out beyond the standard drivetrain coverage period, so you decide what to believe. By the way, there most likely is at least pro-rated warranty from Ford since it had the flash, but that goes away completely at 80k miles. You are buying a used truck, therefore saving money in lieu of having a warranty to pay for things like cam phasers.
So, I guess my advice is that if your "fear" is that it will effect the truck, period, then don't buy an F-150 with anything other that the 2,7L eco-boost motor, as that seems the only one that rarely suffers from the cam phaser issue.