Seamless mobility support in a heterogeneous roaming environment poses several challenging issues in the choice of network architecture design and mobility protocol. Several standards organizations are designing next generation wireless network architectures with a suite of new network elements and protocols that provide service continuity for intraand inter-provider roaming. However, each of these mobility solutions provides its own set of signaling mechanisms and methods of interaction with different functional network elements. Thus, it becomes a challenging task for the network operators and service providers to support roaming to the visited networks with diverse capabilities while supporting service continuity. In this paper, we first highlight some of the next generation standards and then describe the main functional components of a generic next generation wireless architecture as described in several evolving standards. We then focus on the operational usage of network layer mobility protocols such as Client Mobile IP, Proxy Mobile IP and application layer mobility protocol for next generation networks, and address the operational issues associated with roaming and service continuity. Finally, we propose comprehensive mobility solutions that support the heterogeneity associated with the intra- and inter-provider roaming.