License expiry - what happens to the cluster

HA is part of the base license. Therefore the HA will still run. Base license cannot expire. All modules, will be disabled (proxy, web, IPS etc.). Tunnels will still be there. 

Thanks, I actually thought, a license is necessary... But even in the feature description, it is mentioned:

Base Firewall is not a subscription, it is a license valid until year 2999.