Talks have been taking place this year with mobile phone carriers in the U.S. and Europe in regards to bringing cellular connectivity to Apple Watch.
During the discussions, Apple executives expressed concern that the cellular models may not be ready for release this year and that the feature may be pushed back to a later generation, according to the people. Apple warned that, even on an aggressive schedule, the earliest possible shipment time-frame for cellular models would have been this December, one of the people said.
Apparently, the roadblock is that current cellular chips consume too much battery life. This is already a pain point for customers and would limit user appeal. Apple is researching low-power cellular data chips for future generation smartwatches.
Apple's goal is to untether the device from the iPhone but at this point it appears we'll have to wait a little bit longer.