Analyst - GTA IV to sell 13 million copies in 2008

[WiiStation360]

It might be possible.

CoD4 has sold 8.22 Million copies to a combined 29.4 million PS360 owners. (28% attach rate)

Assume that there might be close to 44 million PS360 owners at the end of the year (~20 PS3 & ~24 360). A 28% attach rate for GTA4 would give you 12.32 million copies.