Details about Gran Turismo 5 has been announced! Here is the latest information on the game design:

■ models included
1,000 vehicles
170 Premium new models (full interior modeling, the interior corresponds to vehicle damage)
830 kinds of standard model (some are from Gran Turismo 4 that have been carried over to GT5)

■ Courses
60 courses confirmed with 20 or more to be revealed

■ physical simulation of vehicles
Physics system simulation is brand new
Represented is full fall in vehicles
Damage representation (reproduced in full by real-time collision deformation)
faithfully reproducing the behavior of electric cars, i.e. Prius, Insight, hybrid cars and the latest Tesla model

■ Arcade Mode
Single Race
2 player battle

■ GT Mode
World Map
My Garage
Car Dealer
Tuning Shop (parts, tires)
Car Washes/Oil Change
Race Championship (Series system, point system)
License Test

■ Online
Open Lobby
Text / Voice Chat
Private rooms
Online Photo Album
Online Replay Album
YouTube replay output

■ Photo Mode
Photo Drive (Circuit)
Photo stage (Stage Photo mode only)

■ Gran Turismo TV
Video output to a PSP or PSP Go®
Progressive Download
Improved

user interface
Continuous Play for videos

■ Museums
TheGran Turismo 5 Prologue version, + more information at TGS

■ Sound
Custom soundtracks (Use songs from your PS3 hard-drive)
Dolby Digital 5.1 and 7.1

■

Gran Turismo 5 Prologue, and the same design concept. The icons change color

I got this information from http://www.gtplanet.net/gran-turismo-5-game-features-announced/.

Im really happy about some of the stuff that has been announced, now all Im waiting for is an official realease date :)