I don't believe it will outsell Halo 3. For a myriad of reasons.
- Historically, a huge selling successful title witnesses significantly less sales on it's sequel simply because in order to reach that many sales there was a lot of people who bought into the hype once and won't be fooled again the second time. So while the 'fans' of the series will still buy the game in droves and there are a lot of fans for Halo, it won't hit that high mark that Halo 3 did.
- Secondly, Halo 3 was one of the first few epicly large titles for the Xbox 360 and also was Halo HD.. (Well actually it wasn't but you know what I mean)
. For this reason, anyone associated with the Halo series that remotely enjoyed it went out of their way to go out and purchase this game. This relates to my first point. Less sales because some of the people who went out of their way to go out and purchase this game weren't happy with the direction of it, the gameplay in it , etc and won't get it because of it. A good example for this IMHO would be God of War III. I bet God of War III sells a good amount (For it's series) and most likely more than the other 2 God of Wars sold. But I highly doubt if there was a God of War IV it would sell as much as III because the buzz / hype around it is lessened.
- Thirdly, It was a well established series. So comparisons to Uncharted or a myriad of others don't really apply. Uncharted 1 for example was always an underrated game and received no hype factor for it whatsoever. Uncharted 2 got tons of media time and air time on top of having a core fanbase that loved the first one.
- The Halo name is probably at it's lowest point that it's been since the early days of the franchise. And while Halo Reach can certainly go a great length towards putting it back on top, the failures of ODST / Halo Wars do matter on the sense that they tarnish the Halo brand name and weren't up to traditional Halo standards.
- As has been proven, time and time again...Userbase doesn't have really much of an impact on sales. Good games sell well regardless and have great legs. So while the 360 user base has grown that really shouldn't impact sales one way or another.
