(Brion Vibber vibber@aludra.usc.edu): Right now, all wikis are served from the same IP address on the same machine. If we swap IP addresses, all wikis are served from the same IP address, but now they're all on the other machine. That means we must make provisions to serve all phase 3 wikis on the new machine immediately upon making the switch.
You're right--switching IPs means we have to pre-install all the international wikis on Larousse. That would require leaving them read-only for probably a longer period of time than we'd like.
If, instead, we adjust the DNS, we can individually move each wiki to the new server one at a time or in a bunch, but need to make provisions for each one that we switch to leave the old machine in a non-dangerous state for that wiki while the change propogates (which will be reduced by dropping the TTL ahead of time).
That's probably simpler.