It is being developed but so far there is no indication when it will be released.

Will there be a beta program?

There is not a beta version yet, but there are development versions. If you install a development version (known as Nightly) you will typically get an update every day. Development versions can be unstable, for example since 25th April up to yesterday when a particular bug was fixed the 64 bit development versions were crashing on startup for quite a few people. If you still want to test a development version, you can get the installer for the latest version (firefox-6.0a1.en-US.win64-x86_64.installer.exe) from http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-mozilla-central/ A good place to follow the development progress is in the Mozillazine builds forum - http://forums.mozillazine.org/viewforum.php?f=23