IE 9 Preview 6 is now available.

[blogs.msdn.com...]

From IE Blog:

The popularity of the beta also reflects the early exposure to and extensive impact on IE9 that developers have had. Developers downloaded the first five Platform Previews over 2.5 million times. The sixth Platform Preview of Internet Explorer 9, available now, reflects developer feedback and delivers better performance as well as more standards support, like CSS3’s 2D transforms:

Looks like an RC build will be the next public "full" build and if its anything like this cycle 4-6 weeks out maybe?