A road map for your API, is one of those essential building blocks that can go a long way in building trust with your API consumers. Sharing your plans, helps developers prepare for the future, and better plan for their own road maps, keeping everything potentially in sync.
From my vantage point, a simple, up to date, easily found road map is a building block that benefits both API provider and consumer. Road maps help provider organize their plans, and figure out how they are going to communicate it with the ecosystem, then setting the overall tone for how API consumers will engaging with a platform--both good and bad.
During my regular monitoring of the space, I saw that Microsoft released a pretty slick "Cloud Platform Roadmap", which is yet another sign for me on how Microsoft is stepping up their cloud (API) game. Their interactive road map allows you browse the roadmap by areas like cloud infrastructure or Internet of Things (IoT), and see features that are recently available, public preview, in development, cancelled, or have been archived.
Beyond the core functionality of the road map, I'm impressed that they published a blog post telling why they did it, acknowledging that it will bring visibility into platform operations. Additionally there is a prominent button, providing an email address where you can send your suggestions for the road map, providing evidence of how a roadmap can contribute to the overall feedback loop for an API platform.
Overall, I like the simplicity of the Microsoft cloud platform road map, and it is definitely a healthy building block I'd encourage other API providers to consider offering as well. I'm going to make sure Microsoft's roadmap is one of the examples I cite along the API management line, as part of my overall API life cycle map.