Extrapolating from our experience from two-week deploy cycles and what bugs we find at each stage, would moving to a one-week deploy cycle substantially increase the number of users exposed to really bad bugs?
For instance, if we're currently finding and fixing about 2 deployment blocker bugs per cycle after the mediawiki.org deploy but before the non-Wikipedias deploy, that data might imply that we should structure a 1-week cycle differently -- perhaps with three stages rather than two.