Hi Raja Guru, thanks for the questions.
First, regarding milestones (referencing this doc, for anyone reading along): milestone 2 is complete, milestone 4 is targeted for Q1-2019, and milestone 3 is likely to come in Q2-2019 or later.
Second, regarding migration from Camunda BPM to Zeebe: in comparing the two systems, the points that Daniel and Thorben mentioned in this thread still holds true: Understanding Zeebe. The Quickstart should help give you a sense of the Zeebe API, and it would make sense to take a look at the Quickstart again in mid-October after we’ve released Zeebe 0.12 (which includes a handful of conceptual changes). We don’t yet have an official “migration guide” for Camunda BPM users, but this is something we’ll need to put together in some form as well.
Lastly, if you’d like to talk more about this, feel free to send me an email at firstname.lastname@example.org. We could schedule a call sometime in the coming weeks so I can better answer your questions.