Episode IV Revisited will never be in HD. This is because when Ady did Episode IV Revisited, he used the DVD as he had not gotten access to the HD versions at the time. To make an HD version would require starting from scratch and finding HD sources for other things he used (like the Alderaan explosion, etc.) - not to mention the fact that the original Ep. IV Revisited files no longer exist, making it that much more difficult.

Only ESB:R onward will be in HD, and those will be 720p at maximum because it's too difficult for Ady to find 1080p-quality sources for new things (I'm reminded of an early test shot at 1080p with new Wampa tusks that looked pretty awful because Ady couldn't find good tusks at high enough resolution to work with).

But in the meantime, Ady is releasing color-corrected 1080p AVCHD editions of all six films - ESB was restored to its 1997 SE form, while ANH had the Han/Greedo scene restored to its 1977 original form (the rest is the 04 SE). The rest will be out as he gets the chance to work on them.