One reason might be that the change brings the logo more in line with the Google identity. Google usually doesn’t do shiny and photorealistic, the Chrome logo was always a strange aberration in that respect.

This reminded me of the 2008 Google Reader redesign, where some of the rounded borders and shadows were dropped.

http://googlereader.blogspot.com/2008/12/square-is-new-round...

In the case of the simplified logo, "square is the new round" would seem to apply again.

When do we get the new square Chrome logo? :)

Yes, it certainly seems that way. Recently Google has also changed the logos of gmail, gcal, greader etc and this looks like Chrome's turn.