A Software Product Line (SPL) exploits reuse-in-the-large to enable customization by explicitly modeling commonalities and variabilities of closely related software systems. Delta-Oriented Programming (DOP) is a flexible implementation approach to SPL engineering, which transforms an existing core product to another desired product by applying transformation operations. By capturing product alterations related to configurable functionality within delta modules, DOP closely resembles a natural process of software development, which proves beneficial in early stages of development. However, increasing complexity for a growing SPL in later development stages caused by the invasiveness of DOP drastically impairs maintenance and extensibility. Hence, a process utilizing the invasiveness of DOP in early development stages and restricting it in later stages would allow to mature growing delta-oriented SPL. Moreover, ever-increasing complexity requires means to migrate into less invasive development approaches that are more suited for large-scale configurable applications. To this end, we propose a development process for delta-oriented SPLs including explicit variability points, metrics and refactorings as well as a semi-automatic reengineering of a delta-oriented SPL into a development approach based on blackbox-components. In this paper, we sketch this development process with its constituents and point out required research essential for successfully maturing a delta-oriented SPL.