I'm aware of the other games that needed attention and I am aware that they threw away the GT4 codes, but to be frank, I think PD should quit with the prologue titles. I mean, it's good for some quick cash, but I think it would be better if they were to focus on the main game and polish it up nicely. Then there's no aggravation amongst the fans. I could definitely do without a GT6: Prologue if it will quicken GT6's release.
I think there was an interview were KY said , Prologue wasn't released to show what GT5 will be like but rather what they have done SO FAR. So Prologue isn't a completely different title than GT5, just it's very early version.