As far as I understand you, the 50D is supposed to be a backup body and not a primary. What's the value of a 5D (or whatever new camera you're going to get) if you continue using the old body?![]()
I don't photograph weddings, but I have been doing a fair amount of event photography, and the second camera body for me is not just "backup." I don't know about most people, but I like having two options ready to go, without the need to change lenses. I often keep one on a tripod and use a wireless shutter release that I keep on a lanyard around my neck. Then I can roam around with the other camera, able to take pictures with both cameras no matter where I am. So there's lots of value in having both types of cameras.
I dont see any need to keep the 17-55f/2.8 OR buy the 24-70 with this lineup. Thoughts???
Honestly, for your needs, I don't really see how having IS will be really critical. I need it for my museum work, but a wedding photographer can probably get by without it. If you get the 17-40, that can be your normal zoom on the 50D.