The fast evolution pace for cloud computing software is on a collision course with our growing reliance on cloud computing. On one hand, cloud software must have the agility to evolve rapidly, in order to remain competitive; on the other hand, more and more critical services become dependent on the cloud and demand high availability through firm Service Level Agreements (SLAs) for cloud infrastructures. This race between the needs to increase both the cloud upgrade frequency and the service availability is unsustainable. In this paper we highlight challenges and opportunities for upgrades in the cloud. We survey the release histories of several cloud applications to analyze their evolution pace, and we discuss the shortcomings with current cloud upgrade mechanisms. We outline several solutions for sustaining this evolution while improving availability, by focusing on the novel characteristics of cloud computing. By discussing several promising directions for realizing this vision, we propose a research agenda for the future of software upgrades in the cloud.