Already Halo 3 has an attach rate of 33% (or very close to it). Factor in 7-10 million people who have rented the game, bought used games, etc, the attach rate per unique user would be closer to 60% (we know this data from Major Nelson's reports of unique users, acheivements obtained, etc.). CoD4 has a similar statistic with 12 million unique users that have played the game, and yet only 7 million in sales. This does not mean that 100% of the people who have played Halo 3 will buy Reach, but I would not be surprized that at the end if the number will be in that spectrum (50% of the Xbox community will have Halo Reach in their games played list).
Does this mean that 10 million out of the 40 million people who will have Xbox's will buy Reach in the 1st week? Probably not. BUT 3.8 million out of 11.7 million people did for Halo 3. Thus it certainly is possible (though not likely) that Reach COULD outsell MW2 on Xbox+PS3+PC.
My prediction is that the Arade will be $149, and the Elite will be $249 early next year. Xbox already has tested the market for an Elite for $249 buy offering $50 rebate soon after discounting the price of the elite to $299. This tells us that at any time if they wanted to they could discount the price by $50 without batting an eye. No reason to discount before a holiday season. Walmart and Amazon has already proved that $99 (net) Arcade consoles will fly of the shelves, so it is entirely possible to see a $129 Aracde at some point (maybe with the release of Reach and Natal) later next rear. $129 Arcade with Reach release = 10 million sales week 1.







