Cameron once said he preferred the 1.33:1 version of The Abyss. Maybe that's why the "widescreen" DVDs that have been released are letterboxed, but not anamorphic.
I read an interview with Cameron who didn't understand why people wanted the letterbox version of The Abyss when it was shot in Super 35 and the 1.33:1 version actually showed MORE visual information than the widescreen version did. At the time, it kind of made sense as the best source for video was laserdiscs and the best TVs were still use 480i Standard Definition TVs. Why "waste" your pixels on black bars when a version of the film was available that had everything in the theatrical release PLUS more information on the top and bottom of the screen AND filled the standard TV screen.
However, widescreen HDTVs are now popular (though hardly yet the norm), DVDs look WAY better than laserdiscs PLUS they (mostly) come in anamorphic widescreen, plus there's HD broadcasts and now HD-DVD and Blu-Ray discs, so there's just no reason to release a version that doesn't reflect the theatrical aspect ratio and allow the home theater enthusiast to be able to recreate the theatrical experience as closely as possible. I don't think Cameron would claim a preference for 4:3 video any more.
As far as his original preference being the reason why The Abyss was originally available only in letterboxed 4:3, that doesn't make any sense to me. I think it was made that way because it was easy to re-use the masters from the laserdiscs and since the vast majority of potential buyers did not have HDTVs then, most buyers wouldn't even be able to detect a difference (since letterboxed 4:3 and anamorphic widescreen DVDs look basically the same on SDTVs). That was a stupid decision that showed no foresight to how the market was changing, but a LOT of movie companies were guility of it. Of course, when some movie companies re-released 4:3 letterboxed movies as anamorphic widescreen DVDs, they saw the profit in double-dipping and started released "special" editions and "collector's" editions and "unrated" editions and now are poised to probably do the same double- (and triple- and quadruple-) dipping with high definition DVD formats.
Oh well, what's a collector to do? It's like Tommy Lee Jones said in Men In Black when encountering some new futuristic digital storage media: "Look's like I'll have to buy the 'White Album' again!"