Advertisements I've speculated before that crossing the barrier to/from makes quantum time jumps possibly of unpredictable but usually small duration. When Locke likely 'moves' the Island he'll somehow activate the capability to translate elsewhere and possibly elsewhen by a bit. Not sure there. The Island shields itself from all electromagnetic radiation. Light as a high frequency EM wave is also distorted making spysats ineffective. (We can in the lab today make some objects 'invisible by bending the light from behind them around them and masking the object). Only Desmond's key made the Island briefly unshielded or transmitting. Once the Island is moved by Locke, Jack and the remaining O6 won't be able to find it. Nor will evil robber baron Chuck Widmore. As I see this series finally playing out, there is hope that Jack & Co. may eventually be able to 'get back', because I'll bet that Ben knows how to do so. I have a feeling that whether or not Jack et. al. do successfully return will be left ambiguous in the final series episode, pissing folks off.