PD would need to develop something similar to google earth, but have the entire EARTH rendered to portray something like that... I don't think that would EVER happen
I disagree.
People seem to forget just how far things have moved in recent years regarding global mapping and navigation. Right now, anybody with a computer or suitable mobile phone can download Google Earth and view any part of the planet, and in highly populated areas, view streets down to incredible detail. That's amazing. I can drive along with a SatNav system in my car, tell it where I want to go, and it will guide me there, even if I take a wrong turn. That's amazing too. People are spoiled these days, and don't really appreciate things for what they are.
On top of this, detailed map data for the majority of the worlds major countries is already there, including altitude. A HUGE number of streets and roads have been photographed close-up. Data is piling up as we write, and it is only a matter of time before it all comes together.
Imagine entering your postcode into a game, and then using the map, you highlight a route to race around. Now, racing around that as a plain track is one thing - racing around that track with the scenery around you looking like the real location is quite another. The latter option would take some serious streaming and processing, but is not beyond the realms of possibility. However, just being able to race your local area (or anywhere you choose), with artifical scenery rendered on the fly in-game would be very cool.
It may not happen this decade, or even the next, but I can guarantee that eventually, sufficient data, processing power, and infrastructure will exist to allow a gaming world to be constructed from our own, on the fly. It will play host to racing games, FPS games, flying games...you name it.
About 20 years in the future.
Personally, i see no market for this GPS for GT5 option. Though it does indicate there will be more real life circuits than people are expecting.
Surely though, just because I will not record my own, does not mean I will not be able to play ghosts from others? Take the Top Gear Test Track for example. They could now record actual laps using GPS data and have ghosts for us to race against, not just accurate in terms of time, but also track position etc.