*UPDATE* - BBM 188.8.131.52 has been pulled from BlackBerry Beta Zone for all BB7 devices, only OS5 & 6 are supported for now.
A new BlackBerry Messenger beta build is now available in the BlackBerry Beta Zone. With this release, you'll be bumped up to v184.108.40.206 but the change log for it is rather slim, as noted:
In this latest upgrade, we've focused on bug fixes in platform such as avatar changes in Bridge and enabled a 'Third Party Application' discovery system message.
Issues: When scrolling up to view message history in group chat focus jumps down and makes it hard to scroll
If you're a BlackBerry Beta Zone member you should see the download available now. RIM hasn't sent emails out as of yet but it is showing up for most as being available for download. Thanks, @ABoldGuy!