New Delhi, Oct. 23 -- Every few years, there's a whisper that Apple could upend tablets completely. The latest rumour makes a bold promise, an 18-inch foldable iPad that's as big as a laptop and folds into a compact shell. But recent reports suggest the device is looking less like an imminent revolution and more like a stalled prototype competing with the priciest gadgets ever launched.​

According to Bloomberg and insiders cited by major outlets, Apple's plans centre around an 18-inch OLED screen sourced via Samsung Display, one that's engineered to minimise the crease that plagues most current foldables. But development headaches are mounting. Engineers are grappling with weight, current prototypes reportedly tip the scales at 3.5...