With exactly the same published dimensions, it seems a fair bet that the 50D will indeed fit in 40D housings. This will obviously be to the delight of all 40D housing owners.

As I've got a trip to Thailand coming in six weeks, I really want one before I go. In a desparate attempt to so see if it will fit, I overlayed 40D and 50D images using Photoshop. I'm glad to say that the signs are good, with the only differece being in the bottom left corner. I doubt this will have any consequence. The big question of course is whether the tripod screw is in the right place - though it would seem odd for Canon to change this.

For now, watch this space. I plan to have my hands on one as soon as possible...