The digital transition profoundly transforms spatial behaviors, redefining residential choices and challenging conventional urban planning approaches. This paper critically examines the limitations of current municipal plan sizing methodologies in Italy, which remain based mainly on retrospective demographic analyses and static regulatory frameworks. Focusing on the metropolitan contexts of Rome, Naples, and Florence, the study reveals how existing tools fail to account for emerging dynamics such as smart working, housing mobility, and multidimensional well-being. It argues for the development of updated assessment models and composite indicators that reflect new patterns of settlement and lifestyle. The analysis highlights the increasing appeal of smaller municipalities and emphasizes the need for planning approaches that are more flexible and grounded in real-time data, in order to better respond to shifting residential trends and local development challenges.