Speaking to Joystiq, Microsoft's Frank O'Connor, creative director of 343 Industries, said that he worries "constantly" about the possibility of the market being oversaturated with Halo. When asked about the amount of Halo products out there (namely ODST, upcoming books, more comics, Halo Legends and the recently released encyclopedia), O'Connor said, "I worry about that constantly."
Regarding the various Halo products, O'Connor said, "All of that stuff has existed in the past, and it exists because of one simple reason, which is demand. We wouldn't make it if we weren't continually being asked for it." He added, "We obviously turn down almost infinitely more stuff than we actually produce, but when we produce it there's a good reason and a good plan and a strong demand."
As an example, O'Connor noted Halo Wars Risk, saying that the two games "had a natural connection" and that board game manufacturers actually received requests for a Halo strategy game. Still, he said that 343 has also had requests for things that "don't make any sense." Even if there is a demand, said O'Connor, "If it doesn't actually make sense and it's completely crazy, we won't do it."
Keep an eye out for the full interview later this week.