IoT Hub will be updating the underlying infrastructure and will go through an internal service update to improve reliability for device connections. The update will change the underlying DNS record for IoT Hub, resulting in a change of the IP address.
This update will not have any impact to you if you don't take dependency on the static IP address. To ensure you are not impacted by this service upgrade please follow our best practices regarding IP addresses and use Fully Qualified Domain Name (FQDN) or Service Tags: IoT Hub IP Addresses Best Practices