If you are wondering about the CU schedule then you can check it Via Service Adminsitration Portal.
Please read this FAQ
here are 2 related questions from that FAQ:
Does SharePoint Online apply every Public Update?
SharePoint Online Dedicated customers are organized into 2 patching waves, which means each
customer’s environment will get patched every second published Cumulative Update
How will I be notified of upcoming Cumulative Update deployments?
Notification of all CU deployments will be provided at least 5 working days in advance by the Forward
Schedule of Change (FSC) on your Customer Portal, which can be accessed via the Service