From that we can conclude course maker is coming to GT6 only because it was advertised since the beginning but the "real" version will be coming in GT7.
I agree, GT6 was a mistake.
It makes me sad when I fire GT6 up and see all that potential wasted on a machine as powerful as my microwave oven.
I was thinking about this today and though of what may be brewing.
1. There is a team at PD still working on GT6 features – VGT cars, due to possible contractual obligations. Patches. Maybe the Course Maker. Ideally, this Course Maker would serve as a connectivity beta test for the full fledged GT7 version, since it seems to involve net infrastructure for GPS data, mobile apps and what have you. The client
2. GT Sport / 7 Prologue would be a glorified demo featuring only racing cars, since most of those are already modeled in Premium quality. You could build a compelling racing game with fewer cars and tracks with a more limited scope.
3. GT7 is coming with everything above added to it... one day in 2017.