Supposedly sainsburys are the first to offer sirco, second week in January so would expect the media campaign to coincide with product launch. No point in advertising something that's not available, only upsets the consumer so second week in Jan it is.
They've been gearing up for this for some time so am expecting a very good launch, one of the directors was previously responsible for increasing Red Bull sales from £3M to £130M so he should know a thing or two about selling bottles of juice!