You are right. There is going to be a Business Analyst Online API for Flex released in May. It is going to have similar functionality to the current BAO REST and SOAP APIs and essentially acts as a Flex wrapper around the tasks within the BAO REST API (http://resources.esri.com/businessAnalyst/onlineapis/index.cfm?fa=rest).
I believe you spoke to some of my team members at the Dev summit regarding an interest in the Business Analyst Server API for Flex. We are going to have a BA Server beta release in May. I believe we have your contact information and will include you in our Beta program.
Hope this helps. Let me know if you have any other questions.