I have not seen anything that states that cellular LTE is IN…. the iWatch
but the "paired" IOS device….can communicate via it's own cellular radio…which has 2G/3G/ and in some cases 4G LTE. It then communicates back to the iWatch via low power radio….
think about your bluetooth headset….but with a wrist display to send and receive information to/from the phone and internet. Some of the smart watches are also gathering information from you (heart rate and other biometrics)…