Seems official, Garmin is not doing any further development on the Mapsource program and is instead concentrating on developing BaseCamp (argh!)http://gpstracklog.com/2011/08/goodbye-mapsource.html
I do all of my route planning and track editing in MapSource, and this is going to be a bummer to me. I have tried BaseCamp, and as of now, it does not have the capabilities or simplicity of use that comes with MapSource. Hopefully, Garmin will speed up development of BC, particularly with respect to editing tracks.