As a relatively new technology in comparison with traditional push-based (e.g., RTSP-based) adaptive streaming techniques, deployment of HTTP adaptive streaming (HAS) presents several technical challenges. In particular, enabling optimized delivery of HAS services over wireless networks requires developing specialized end-to-end architectures and algorithms for enhancing service capacity and user QoE. A few research vectors in this space include: (i) HAS-specific adaptation at the client and server, (ii) HAS-specific QoS delivery and service adaptation, and, (iii) HAS-specific transport optimizations over heterogeneous networks. We will present some of our ongoing work on these topics with a focus on 3GPP networks and discuss future research and standardization opportunities.