For 5D i think your’e safe buying now. Check out this buy guide:
http://www.canonrumors.com/cameras/canon-rumors-price-watch/
But they are going to announce stuff in Sept:
http://www.ubergizmo.com/15/archives/2010/08/canon_set_to_announce_new_cameras_for_photokina_event.html
And the MKII was originally announced in Sept 2008.
Probably not really helpful from my end. This was just from a quick Google.