I've notified senior staff, but beyond the domain expiring your sites/accounts are still hosted with us and are 100% intact - the server itself is still there, just that the domain used to access the sites expired. Given the expiration date, it should be in the recovery period so senior staff should be able to easily recover it.
The absolute worst that'd happen is having to get everyone a .x10host.com or .x10.mx subdomain, but given that said staff just renewed it while I was typing this, it should all sort itself out in a few hours once the DNS records re-propagate and update