They wouldn't have to expose the servers to the web to create an archive. In fact, it's more difficult then, because the database(s) are going to be written to while they're trying to copy the data. Surely they didn't expect ALL OF US to just GO AWAY and not try to log into them in the morning, right?
I suspect someone was given the word to post the "shutdown" notice, but they'll keep them alive as long as possible, just so we can each do our own selective archiving of important posts and information. If the server management is paid and the bandwidth is there, it is pointless to arbitrarily turn off servers.