Considering the post above, along with the lack of updates for Garmin's other mapping software, makes me wonder if BaseCamp is being turned into Garmin's defacto successor to the others?
Not "being turned into". It already is.
I'm wondering if anyone who is familiar with all these various different Garmin programs can help me sort through what seems like a confusing assortment of different programs, some still available, others not.
MapInstall does what it says. It will allow you to select map segments or entire map products and install them to Garmin's personal navigation devices (PND). (Mapsource contains this functionality built in. Basecamp does not.)
POILoader also does what it says. It allows you to load custom POIs onto Garmin PNDs. So you can download POI files from sites like POI Factory and load them onto a Garmin device.