Having read through come of the questions on here it's my understanding that v 1.0 of the API is for read-only access to real-time data, pretty much what's available in the data dump. Write support is planned for version 2.0. My question is, will version 2.0, or some future version after that, have a means to access the chat system? Specifically, what I'm looking for is a way for Stack Apps to authenticate as a user and post messages to a Stack Exchange chat room. Is such functionality planned?
Its too early to call this, as the chat system is still evolving.
However, exposing the inbox is planned and since some chat events are published to the inbox there will be at least some exposure of chat events.