From the Garmin Forums Website :
I’ll create a case for better via-point routing in BaseCamp. The distinction between announced and unannounced via-points has always been a bit too subtle for me (and I assume a lot of our users). So hopefully there is something we can do about this.
And I am sorry to disappoint, but yes, MapSource has not been worked on in quite a while, and there will be no new releases of that software.
You are of course welcome to keep using MapSource, we will keep it on the website for the foreseeable future.
Basecamp is the the Mapsource replacement. It does bring new functionality not found in MapSource, like the ability to download and transfer BirdsEye imagery. This maybe a good time to download a copy of Basecamp software. One major difference between BaseCamp and Mapsource is that BaseCamp will use the maps on your Nuvi and doesn’t require a copy of the maps to be on the PC as Mapsource does. There is also a PC and MAC version of Basecamp.
Download Garmin Basecamp here