Move to S/4HANA now, or wait?
The move is coming either way. The timing is the real decision. S/4HANA earns it when the close, the reporting, and the process debt are costing you today. Waiting can be right too, when ECC is stable and the bigger fire is somewhere else. Either way, the answer should come from an assessment of your code, data, and interfaces, not from a license renewal date.
Waiting is a legitimate strategy, but it needs a date attached. The assessment sizes your custom code, data volumes, and interfaces so the wait is a decision, not a drift.