Update: Someone at the Tor project kind-of-answered my question about the expiration of the consensus interval a moment ago here:
"If four out of the 9 dir auths were compromised and taken offline, then the remaining 5 will continuing publishing the consensus and the network will continue operating normally. If more than 5 are taken offline then this was a horrendously large operation and the necessary corrective actions will be taken to ensure the network remains operational." https://blog.torproject.org/blog/possible-upcoming-attempts-...
"If four out of the 9 dir auths were compromised and taken offline, then the remaining 5 will continuing publishing the consensus and the network will continue operating normally. If more than 5 are taken offline then this was a horrendously large operation and the necessary corrective actions will be taken to ensure the network remains operational." https://blog.torproject.org/blog/possible-upcoming-attempts-...