Personally I think GS is a bit "year 2000". It never saw proper, rapid and dedicated development. It feels and looks like a side project. Since its stuck in a corporate setting, don't get your hopes up about it going open source. I don't think it will die completely, since its a nice intro to game development. But Im sure we will see less and less people using it for bigger projects. The pipeline for every facet of the toolset is severely outdated. It just isn't a serious toolset.

Unity has a free version with which you can make commercial games. Sure it lacks the advanced features, but you still get that amazing pipeline and ease of use. The only thing that will truly save GS is if they make everything up to the commercial license freeware, and start updating everything very quickly.

edit: As for the price, $1500 for unity pro is crazy good, if you look at what you get. Comparatively, GS PRO should cost about $200. Its overpriced.