Apparently, this is the case. RIM sent out an email to all of the BlackBerry smartphone carriers stating that “all versions of BlackBerry Desktop Manager prior to version 4.5 have been removed”. One could speculate that this is probably just a clean-up effort, especially since there were versions that dated all the way back to 4.0 on some websites. This should help decrease the confusion users face when downloading the software and could also reduce the number of people who download incompatible versions by mistake. There should be no confusion on the RIM download page though, because they are only offering 5.0 versions.
And for you Microsoft Outlook 2000 users, it seems as if you will no longer have synchronization support from BlackBerry Desktop Manager. Support for this version of MS Outlook has been removed from BlackBerry DM versions 4.3 – 5.0. Head here for more info.