At this point in time, the development team is at the end of the current sprint. Hence, the sprint backlog of the coming sprint doesn’t exist. But the product backlog does. Moreover, the development team cannot dictate which story points to prioritize . They need the say of the product owner. In turn, the product owner prioritizes only the items in the product backlog. In summary, under the given conditions,it looks the product backlog is the place for the process improvement effort than sprint backlog