I'm not sure on the cost yet but it will not be free to upgrade from 3.x to 4.x. The limited license price only covers updates for the current version. i.e: 3.0 to 3.9 or 4.0 to 4.9 etc.
I think you are talking about a reduced upgrade fee , no? I'm not sure that discount will ever apply to the limited license, but I was discussing the possibility of getting discount on commercial (single title) licenses for existing customers of either limited or commercial licenses.
* There really should have been a note added somewhere telling people to hold off on buying the limited license, if they plan on getting 4.0. -oops.