I voted yes, not because I think they should implement this feature right away - they shouldn't - but because I think it would be great in the future - they should at some point in the future when they can afford to.
The thing about Free Roam though, is what it entails. Being forced to drive around town slowly at the speed limit all the time would make this mode tedious and overly restrictive; not too good for something called "free roam". But I'm getting ahead of myself, and the main issue: where? where are we roaming? Around towns and cities? Or around tracks already implemented in the game, where you can cruise the outskirts and drive through the infield area, for example. But to base all the gameplay around a free roam mode ala recent Need for Speed games... I just don't know. Allow me to indulge my imagination.
I think implementing free roam as an extra would be more wise, give us the option to take our cars out for a drive. But give us some interesting places to go. Make in game traffic laws for cities and most roads, but allow us to break them, with maybe a simplistic police force that will chase you in slow cop cars and vans, allowing for Getaway in Stockholm-style fun. Of course, another draw for this mode is for photography - as someone else said, being able to stop and take pictures wherever and whenever they want would be sweet too. I'd love to book it down the highway in a veyron, do a brake test, get out and take a picture of the cops barrelling down the road on the horizon, then get back in the car and continue running away! Basically, we should be allowed to create our own fun.
Seeing as GT allows for a variety of racing environments, why not allow for a variety of driving environments? Offer us cities, tracks, and middle-of-nowhere roads, highways, freeways, and any strip of two-lane heaven in between. Allow us to adjust the traffic, or the option of a dynamic or fixed setup where traffic thins out at night and congests in the morning depending on location. Or both.
Here you go: implement one big free-roam mode where all the games' circuits and cities are interconnected with roads through a variety of real-world environments. I think it would be unfeasible to try to cram the entirety of planet earth into GT, though maybe in 50 years on PS15 we could see that. Instead you'd be driving around a sort of 'serious' San Andreas on a yet larger scale with much more elaborate and varied roads, "continents" interconnected by huge and awesome bridges that curve and swoop unnecessarily like a roller coaster, just for a bit of fun and challenge (That's an idea of its own that has serious potential for premium gameplay). You'd have gas stations and garages everywhere as safe points where you can refuel and repair your car, but otherwise the entire point would be recreational driving, long or short distance, in any car. You would be completely free to drive anywhere you can physically go. I can see huge appeal in this - especially if you can take this mode online (O.O), but for the PS3, it's little more than a pipe-dream. I do think Kaz should consider waiting before attemping to put a free mode into Gran Turismo, there's too many problems to fix first.
After all, who wants to do this sweet free-roam in a standard car, with no cockpit view and no high-beams? And no rims? Speaking of which, how many players would ignore such a mode knowing they can't really show their cars off in an online environment without a decent set of customization options? And I don't think it'd work too well if only a handful of free roam areas are affected by daytime and weather cycles, that might be both confusing and infuriating.