Wow, I can't believe some of the comments here, people seriously need to go take a crack at modelling and texturing a whole premium car themselves before they say that they should be given away for free.
The bottom line is vote with your wallet though. But I think some sort of subscription would be a neat idea.. I think they should have done it for GT5

, gradually release new content to keep the game fresh.
Maybe even at the end of GT5's life give subscribers a big discount on GT6 and their PS4.
Or they could just do like iRacing and charge a subscription plus extra for each car and track. For the amount of content GT5 offers, it's a steal.