BV, you know there are so many LE copies left because there were so many of them made. It was not limited in the sense that it was rarer than the regular version, it was their way of milking a little more money out of it. I'm sure they didn't stop producing them after the first run.
It has sold more than 7 million copies, and this statistic is from November 9, 2005 (one year after it launched).
http://www.bungie.net/News/TopStory.aspx?story=h2anniversary
Yes, selling 2.4 million in 24 hours and 4.6 million copies in the year following is terrible. I'm sure Nintendo has a game that puts that to shame.
On topic, dashboard chat between Xbox 1 and the 360 can't happen, at least not yet.