The roadmap is driven by a number of factors such as developer feedback, User Voice feature requests and Xero's internal product goals. Priorities and circumstances are constantly changing so please use the roadmap as an insight into our current plans rather than a binding commitment.
Whenever we make a change to the API we try to do so in an additive way that won't break existing integrations. However, occasionally things can change in a way that isn't backwards compatible. Make sure that you stay in touch so we can let you know when things do.