Would you then be able get even better 16:9 using an anamorphic adapter?

Completely theoretical, so impossible to state an absolute answer.

Anamorphic adapters introduce difficulties of their own (astigmatism, primarily, but also limitations on use of filters and other such). However, a full-surface-of-the-chip XL2 with an anamorphic adapter would maybe provide higher quality... we don't know, because the chip is megapixel already and we don't know what compromises in the image there will be from that decision. However, it'd be fairly easy to judge once the camera comes out: put a DVX/anamorphic up against an XL2/native and if there's a significant picture quality difference (assumedly in the DVX's favor) then the answer to your question would probably be "yes". If there's no discernable difference, or if the XL2 is better, then the answer would likely be "no".

Hmmm.... I don't think this test is ok. Because is not posible to use whole chip.`In 4:3 you use the center arrea (with lines of pixels turned off above, beneath and lateral of this arrea) and in 16:9 you still get lines of pixels turned off above and beneath the used arrea.
I read that canon will provide an SDK kit for programers. Maybe this way someone could activate&use the all area of the chip? (you'd also get a wider pic).

The SDK will do many things, but I seriously doubt that it'll activate non-firing pixels.

But it would be nice!
And if you could get all that raw data out from the big (resolution) CCD to a computer... :)

I wonder if you could turn it into a 4:4:4 camera.

You know, that SDK could mean a lot! I'm positive we'll see some third party apps for this camcorder! Those apps will be in your accesories bag with the tripod and all! :)
Does anyone know about any other camcorder with such a feature? I'm curios what others have done with that camcorder!

Although it could also be a useless feature! I mean, in a Sony, where you get all kind of features software disabled, an SDK could bring it all to life! But Canon gives you all from the begining! So maybe an SDK would not necessary bring new features to the camcorder! :)