A folding iPhone risky because it "would cannibalize existing iPhone sales"???
Why would Apple care, if they sell fewer regular iPhones and more folding iPhones so they sell the same number that's just as good. The fact a folding iPhone would undoubtedly cost more so even if the margins are the same the profit per phone would be higher. That part would be a win/win.
The risk is that it develops problems over time like a visible seam where it folds or some type of mechanical failure. Plus there's the risk that if it is a niche product like folding phones currently are it may not be worth their trouble to design & sell it. They quit making the iPhone "mini" because it wasn't selling enough despite it selling quite a few more units than all the folding phones from all the Android OEMs combined. If they ever start making a folding iPhone they want to be sure it sticks around or they will piss off customers if they discontinue it after a couple years.
I don't really have much desire for a folding phone, but that seems much more useful than a folding tablet. At least a folding phone allows a bigger screen that what would fit in your pocket otherwise. I don't really see a reason why I should want a tablet to fold to a smaller size, but I guess the draw is that at a 90* fold its form factor is basically that of a laptop and can sit on its own (but then why the mention of the stand in other articles...maybe I'm not understanding what the target market is for this)