It will possibly be heavily bundled at the end of this Year, a GT5/LBP2 bundle would be great for the PS3 IMO... Very appealing to the casual customer.
Anyway...
As for the level of bundling, and how it can help out a game. Take Forza 3 as an example. Same genre. The competitions big racer. This Holiday season it was bundled with the 360 with the Alan Wake card. It sold 1.35 Million units with that bundle. That's... Huge. Gran Turismo 5 being a bigger name globally could do those numbers, probably more, if Sony pushed the bundles out enough.
I don't think they will, personally.
We should (Could) be looking at about or over 8.5 Million copies of GT5 by the end of the Year. If Sony bundle it. It's a big if though, as we all know Sony don't exactly do "brainy".
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