From the Adobe Flash Platform Blog, earlier today:
There will not be a beta for Flash Professional CS5
Adobe is no longer planning to release a public beta of Adobe Flash Professional CS5. This is a change from the plan that we announced in October at Adobe MAX 2009….
We understand that some people will be disappointed. Many of us were looking forward to a beta. But in the end, we think that what is most important is to get the release version completed and in your hands as quickly as possible.
Unrelatedly, Corona SDK 1.0 is still available at its introductory price of $99.