Apple is preparing to manufacture its largest-ever iPad, one which will feature a screen measuring 12.9 inches diagonally, Bloomberg reports, with an in-store launch expected sometime early next year. Apple currently sells iPads with 9.7-inch and 7.9-inch displays, but has been working with its suppliers over the past year to develop a range of larger touch-screen devices. Revenue for the iPad has declined for two straight quarters, and some experts believe releasing a larger-screen device will only give sales an incremental boost.