It's not going to happen until Sky allow more channels. The problem stopping them is the one that nearly caused ITV3 to not launch on Sky.
Hmm - are you saying Sky are currently refusing to allow new channels , that are looking after their own transmission , access to the EPG (which is an Ofcom - I think - regulated issue) - or are you saying that Sky aren't currently offering any spare uplink capacity on their transponders (remembering that they don't come close to owning all the transponders available at 28.2) ?
Wasn't the ITV3 issue tied up with ITVs encryption and regionalisation contract running out and ITV and BSkyB not agreeing terms? AIUI this is why ITV2 went from pay-TV to FTA on DSat (it was always FTA on DTT). ITV1 remains FTV (not FTA) on DSat, and ITV3 launched FTA.