Realistically, the pool of people who will be able to effectively work on the image transfer is limited, and will not include more casual users who notice the red links. We're doing a huge amount of work on the transfer right now, but won't be ready to shut down wts and Shared by Tuesday--that will make it much, much harder to do the necessary work: (1. check and tag images on the original repositories, 2. transfer tagged images to Commons, 3. review transferred images on Commons and make sure they are properly categorized.) Disabling edits to wts and Shared will halt tagging and deletion of irrelevant files there, tying our hands behind our backs.
I also think that people might be underestimating the quality of work done on WV and WT in ensuring that images are not copyright violations. In the thousands of images we've tagged in the past several days, we've really run into only a couple dozen images that required outright deletion. Many images are "not free enough" for Commons, and will need to be transferred to local WV language versions under a non-free content policy (under discussion), but again, this will be an easier task if the repositories are still editable.
I don't really understand why the WMF is unwilling to keep the repositories around while we do all this work (some prior discussion with the community might have acted as a useful sanity check...), but the facts that a read-only status would impede the transfer process and that the site-wide broken image links would make the project look bush league make it seem worth delaying the move to the WMF altogether. Unless the WMF is willing to reconsider how to handle this.
-Peter