Recently, Hudson Square Research analyst Daniel Ernst predicted that Rockstar North's Grand Theft Auto 4 (Xbox 360, PlayStation 3) could sell 13 million copies this year.

However, not all analysts feel the same way. Wedbush Morgan's Michael Pachter said that, based on his numbers and figures, GTA 4 might sell at a slightly lower rate than what the others have predicted.

Pachter said that while hitting this number is possible, his estimated installed base of 16.3 million PlayStation 3s and 21.3 million Xbox 360s at the end of the year coupled by his guess for the upcoming video game's attach rate tell a different story:

In my view, the game will be hard pressed to capture 33 percent share of all consoles in the addressable market, and the 13 million estimate from Hudson Square implies a 35 percent attach rate.

To further justify his statements, he cited that Halo 3 (52% attach rate) sold 5.04 million units since launch and Gears of War (28.5% attach rate) sold 2.74 million. He then proceeded to make his prediction on Rockstar North's upcoming game, "my guess is that GTA IV will attach at closer to a 30 percent rate than to a 50 percent attach rate, but it’s certainly reasonable to think differently."

And so, we're down to two basic facts: Daniel Ernst says 35% attach rate (based on Pachter's numbers of user base), while Pachter says it'll actually just be 30%.

We're going to have to wait whose predictions hold true once GTA IV gets released this April 29. 'Til then, keep checking back here for more updates.

Buy: [GTA IV (PS3)]
Buy: [GTA IV (Xbox 360)]