As to my knowledge, George Lucas mentioned that he plans to make an "Archive Edition" of the hexology, where he plans to put all the six movies up to par special effects and canon-wise as he sees fit. This will (finally) be his last word on how he wants people to see the StarWars saga. Fans anticipate that it might be released in 2007, as that is the 30th anniversary of it all.

I think not buying the SE dvds is not such a great loss, after all it will just be 'another roughcut' in a few years. But unlike most OT fans, SE fans will have had their chance to get it on DVD. Oh well, Life's a bitch sometimes.

Edit: I don't think the 2004 release is due to fan pressure, it's just a marketing move to give Episode III a bigger momentum in 2005.