If the "RPG as a loss leader" theory is really the case, then perhaps it is in Hasbro's benefit to have new editions whether they will actually increase sales or not. It gets people's attention, has them thinking about D&D, and even if the fanbase as a whole decides to remain with what they have rather than buy the new edition they would still buy the peripheral products with the new edition driving up the number of peripheral products sold.
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I'd be skeptical that would actually work as a loss leader, though. I am not a good example as I don't consume ancillary D&D products. So, I could be totally wrong.
But, I expect if people aren't playing/reading the new Forgotten Realms, Dark Sun, Eberron, etc. books they are a lot less likely to be consuming the novels, games, miniatures, etc. base don them. This gives some weight to Darqueseid's suggestion, I think. Multiple settings, even if they aren't all that different -- Birthright isn't all that different from classic fantasy or from Forgotten Realms, it is just awesome -- offer more vectors to deliver novels, computer games, etc. Although D&D has been pretty quiet on the computer game front.
All that being said, I will reiterate that I would not expect much business acumen. Barring super intelligent investment strategies, I would always suggest that the best way to make a business profitable is to make and produce a good product. Make a better mousetrap. D&D doesn't have the clout it used to as a brand, so they have to stand or fall sales-wise based on the quality of the product. And, the materials so far haven't been very encouraging. I am sure that they would like to make a good product, I don't expect they are deliberately sabotaging it or anything. It just seems that they don't have the skills or approach necessary to do so.
EDITed to actually say what I meant.