OVER 9000!
Wait, what are we asking here? Is this lifetime, or 24 hours, first week, first month? 5-6 lifetime is NOT unrealistic. It could get as high as 10 million. I believe saying it will go as high as 15 million, unless bundled heavily, would be pushing it. I say this because of the diversity of owners on the PS3. People who bought a PS3 as a Blu-Ray player are not guaranteed to want GT5.