Answering an earnings call, GameStop exec David W. Carlson reveals the release of four major titles by October and November. Noting that GameStop is a US retailer, the only conclusion we can make out of the info is that the release margins are for the US, and we can only speculate on how it's gonna be for other regions.

Here's what he said, responding to a query on new titles:

Yes, the new title base actually looks very very strong for the second half starting in the fall obviously with Madden, Rock Band Beatles, you’ve got Guitar Hero 5, the new Halo 3, and Batman as I said earlier, and then going into October with Tekken 6 and BioShock 2, and then going into November with Call of Duty: Modern Warfare 2, Assassin’s Creed 2, and we believe there’s a couple of Nintendo titles coming that have not been announced. So, it looks like actually a very very strong fall and holiday season.

So based on what Carlson has said, it's October for Tekken 6 and BioShock 2. For November, it'll be Modern Warfare 2 and Assassin's Creed 2 plus a few unannounced Nintendo titles. We already know Modern Warfare 2 is due out on November 10th, while BioShock 2 has a vague Q4 '09.

Given that those four titles are multi-platformers, it's not clear if all versions would come out all at the same time, especially for Tekken 6, which has a PSP version that the three other titles do not have.

Should there be differences in the platform releases, it's unlikely that they'd be far apart anyway.

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More release information:

• Assassin's Creed II to be released during the holidays
• Tekken 6 PSP is official, first screenshots