Read about it here.

Version 4.9.2 is intended to be the last 4.x release of DotNetNuke, and this one is called the Community Edition.  That is to be distinguished from the Professional Edition of DotNetNuke.

Next Monday should see the release of Version 5.0.1, a "stabilization" release of the 5.x version.  This will also be a Community Edition release.

For those interested in 5.x, I'd recommend waiting at least a week or two to see what problems crop up in this release.  But, from what I read it seems to have fixed all or most of the major flaws in 5.0.0.