Loads of DVDs are slightly reframed from the theatrical or previous home video versions, but it doesn't alter the aspect ratio. 2.40:1 is still 2.40:1. Sure there's less information present than in previous releases (I compared it when this thread showed up on Millienniumfalcon.com, and even posted a couple of pics), but it's almost certainly intentional and the ratio hasn't changed (although the image is slightly cropped). There's a good featurette on this sort of thing on the Seven DVD. It goes into detail about how shots are reframed and how scenes are colour corrected according to the director's wishes.

It's all about the framing and what the director wants you to see. Lucas could well have changed his mind (and I think the composition of the cramped shot looks better). The prequels (well Eps II and II anyway) were shot at 1.78:1 but composed for 2.40:1. There are many more things to worry about than this, such as the incorrectly coloured lightsabers and audio glitches. Those are undeniable mistakes (no matter how much Lucasfilm try to deny them). If you watch the Empire of Dreams documentary there are many shots where the lightsabers look perfect, yet they're wrong in the films. I'll be interested to see when and if a 'corrected' boxed set is quietly rolled out at a later date. They can't very well fix it after they claimed the faults with the existing set were intentional, at least not without opening themselves up to a lot of flack...