Hi all,
For anyone with a 50D and wanting an L bracket, Really Right Stuff have updated their web site to list a 50D specific bracket
B50D-L and are accepting pre-orders.
For anyone with a 40D bracket (or who can't wait) I can verify having tried it that the 40D bracket fits a 50D, but it's a less than ideal fit due to the increased length of the rubber interface (USB, remote, etc) covers. I'm not the first person to discover this: example pictures at a blog posting
here.
Giles
P.S. I have no commercial affiliation with RRS or their competitors, other than as a paying customer.