Janco Partners' Mike Hickey estimates 4.4 million Halo 3 units sold in its first week, noting that the figure corresponds to a 67% attach rate to U.S. Xbox 360s and 46% for Europe and the U.S. combined. That's far higher than the 3.3 million units Halo 2 sold in its first three weeks -- a mere 30% attach rate to the U.S. Xbox installed base at the time.
Saying that even anticipating a 20% attach rate for GTA IV was exceedingly conservative, Hickey noted that while it may not reach the 46% rate Halo 3 achieved, even a 30% attach rate would mean first week sales of 6.2 million units -- far above Halo's own.
"If the upcoming release of GTA IV attached at the same rate as Halo 3," said Hickey, "the title could conceivably ship 9.5 million units of game in the first week, producing an astonishing $466 million in sales," concluding that the title, despite the delay, could have a "profound impact" on Take-Two relative to current financial projections.