I tend to agree that the northern runway at Gatwick is a smokescreen.....the environmental lobby would be so hard that it'd never happen. However, the "close parallel runway" to the south would minimise the environmental effects, whilst still giving a significant boost to capacity (even though not as much capacity as a runway at a greater distance).
STN has to be the preferred option, given the amount of land owned by the BAA, the infrastructure improvements currently being completed in terms of road access, the 'modular' concept to the terminal (which could pretty much be expanded ad infinitum), etc.
The original 'announcement' of up to 4 new runways for STN was clearly a 'worst case' scenario, and no doubt under environmental pressure this will be reduced to just 1 or 2 new runways! I'm convinced the government has already made up its mind with STN the preferred option.
All we need now is a decent rail transport policy which links airports without having to sit on a coach on the M25 !