I would but I voted maybe for two reasons:
1. Given the GT5 precedent, I don't believe PD will deliver. They took a long time to release the first DLC pack and when they said DLC would be released every third month and their promise ended up being hollow. Buying a season pass requires you to have trust on the developer and, after GT5, I don't trust PD.
2. Every DLC pack had a car I didn't liked and wouldn't have payed for if they had been sold individually. From the DLC pack 1, the Beetle and from the DLC pack 2 the Leaf. Same with the 3rd DLC pack from which I only bought 1 car, the HSV SuperGT, because the other two were almost duplicates of cars already in game. I don't want to end up paying for two of PDs known favorites: Odd cars few people are interested in (Though I would pay to have that sweet Benz three-wheeler again!!!) and duplicate cars.