Today, Enterprises act in an increasingly interconnected world and in different kinds of collaborative networks. They are part of business ecosystems in which they interact with their customers, partners and competitors. The processes of analyzing and planning the intertwinement of business and IT architecture within enterprises has been successfully supported by enterprise architecture management (EAM) approaches. In this paper, we analyze four cases from different industries (health care, logistics, retail, and education) and argue that the intra-organizational concepts of enterprise architectures (EA) and EAM need to be extended to grasp the challenges of the enterprises' interconnectedness. Beyond the known concepts of extended enterprise architecture and federated architectures, we define five stages of extended architectures. Additionally, we describe challenges and existing solutions, which are relevant for this extended perspective.