Your CSP-PO certification is good for two years. The process for renewal is currently being determined. Expect to receive details about the renewal process in the near future.
In the future, those receiving both CSP® badges (CSP-SM™ and CSP-PO™) can choose to renew one or both, and meet the renewal requirements (and pay fees) for one or both. Scrum Alliance® will send you detailed communication when these changes go into effect.