Hi Greg,
The 30-day expiration period is defined in the trial terms and conditions. See the last tab in the solution details. After expiration SAP CAL will block the creation of new instances but will not terminate the existing instance automatically not to loose irreversibly the changes done during these 30 days.
After expiration you'll need to choose between terminating the instance and ordering the required licenses and the SAP CAL subscription to continue with the S/4 HANA without the trial limitations. It is relatively easy for partners to get TDD licenses.
Currently it is not possible to migrate the trial instance and you'll need to create a new one from the equivalent paid solution and then export/import the changes by yourself. We work on making this transition easier.
The cost forecast takes into account the resources and the schedule but not the subscription status.
Best regards,
Stanimir