First, this poll is horribly designed.
-Options 1 and 6 are the same thing, and could easily be consolidated as "Yes, I'd buy GT6 regardless of what platform it's for."
-Option 4 assumes that people would only have the ability to purchase one driving game, which is logically false because any person with the ability to purchase DriveClub and a PS4 at/near launch would also likely have the ability to purchase those and a PS3 game.
-I could go on, but whatever...
Anyway, I voted Option 1, though Option 6 was just as valid. Unless GT6 has less than 100 cars and like 5 tracks, and/or looks and feels like a PS1 game, I'd see no reason not to. GT3 was in my opinion a big step backwards for the series, despite the much improved physics and graphics engine, and I've yet to get tired of GT5 (often seen as the biggest disappointment of the series).
Also, I have no intention of picking up a PS4 at/near launch, regardless of whatever titles may come out. GT6-as-a-PS4-Launch-Title could have every car ever made, every real course in the world, and every fantasy course from all previous games. It can wait. In my opinion, buying a console (especially these days) at launch is foolish: prices will drop within 6-12 months, the software library will expand, and most importantly you don't get to play test dummy for the hardware. Will I eventually get a PS4 and whatever inevitable GT title there is for that console? Absolutely...but probably not until a year or so after its release.