These are the same films, just in different lineups I believe. They're releasing them the same way they did the last three sets (a set every few weeks) I think. Expect them all out by Christmas, then they'll continue to be available for purchase until Die another Day comes out on DVD. Then, after a couple of months, they'll probably vault them again, kind of like Disney.
These are VERY good special editions. Lots of neat features (I think the goldfinger one has the original radio promos for it) and really cool animated menus. No Bond fan should be without them.
And like someone said, they'll go for exhorbant amounts when they're vaulted again. I'll probably pick up a couple sets, one to watch and one to sell later.
The individual films are also available. Bestbuy had them for $12.50 each, which is very good considering what you get