Sadly, owners of Half Life 2 and its episode 1 sequel won't be able to purchase episode 2 without buying the 2 aforementioned titles, but they can still resell them separately.
Initially, Valve planned to offer 2 "boxes" of episode 2. The black box offered episode 2, Portal and Team Fortress 2, while the orange box added Half Life 2 and episode 1 to the offering. But, Valve has decided to cut the black box off, thus forcing Half Life 2 fans to (re)purchase it as well as episode 1 if they wish to continue their 10 years long adventure. No details were given about the steam downloadable version, but expect episode 2 to be available separately on steam.
"Those who purchase the PC version of The Orange Box will get three separate Steam product codes: One for the three new games, one for HL2, and one for Episode One. This way a PC Orange Box owner can give away their Half-Life 2 or Episode One unused Steam product codes if they don't need a copy of those games. We are excited to deliver the highest value of new gaming content ever offered in one box", said Doug Lombardi, Valve's director of marketing.
The Orange Box will be available on the PC for $49.99 as well as the 360 and PS3 for $ 59.99,$10 more expensive than the deceased black box.