I'm a huge Metal Gear Solid fan so let me state that first. I can see the game only doing around the 2 million mark in the first year. After that the game will likely sell more and more as word of mouth goes around but at the same time it may end up blowing though 4+ million right off the bat due to the extreme levels of hype. MGS games sell well but they also don't. They are a very tough sell that has a HUGE dedicated fan base, the game itself however is not the most accessible game and from my experience is nearly impossible for a casual gamer to play or get into.
You can see a brief sales break down here http://www.vgchartz.com/gamedb/?name=Metal+Gear+Solid
They are fantastic games and one of my top 2 equally all time favorites series :D However they are also one the few (many) games that are dedicated to hardcore gamers and do not have casuals in mind. The gameplay, story, and concepts are not accessible to people who casually play games and throw on CoD, Fifa, or GTA every now and then while they smoke one.
