The tech flood just doesn't seem to stop, does it? Microsoft has just unveiled a new Surface Book that it unabashedly compares with Apple's MacBook Pro. But in just a few days, Apple might be firing back with a computer that Microsoft doesn't have a competitor to. At least not yet. Yes, it might be time for that iMac refresh. Sources are now claiming that Apple is preparing to launch its new 21.5-inch iMacs that have long been believed to sport a 4K resolution, finally bringing the smaller iMac forward in display tech.