They can make a lot of money on PC Nameless

just look at civilization, bad company 2 and starcraft II to name but three games this years which have oll sold exceptionally well on PC. Considering the PC install base is around 250m gamers, there's a huge market for a truly amazing game.
In the end crysis 1 was just too demanding, and you know what media is like: 'zomg you can't run crysis unless it's a beast of a machine!1!!' even though it can run on medium with a toaster and still look good. But also, apart from that, many players found the game itself not that interesting (although i think it's quite fun). It did sell ok though and shifted about 2-3 million copies or so since 2007. However, crysis is a far cry from half life episode 2 which came out that year. It looked far better, granted, but episode 2 just blows crysis out of the water.
They'll just make a bit more money for a little more effort with multiplatform is all.