Mustrum_Ridcully
Legend
I suspect the real thing to look at for WotC is: How many people are buying our current books.
Most people probably buy the new core rules. But even among the devoted fanboys, not all later supplements are bought. They get to specific, or the old books have hardly seen enough use yet.
So what can be done about it? Produce a new edition. Even if you still love the previous edition and have stuff unexplored there, this new edition may come with entirely new and interesting concepts. They are a breath of fresh air, and there is a perceived good reason to buy them even if your previous edition isn't "finished yet" for you.
3E may have had a unique situation - it did it after a really long running edition where not much new came out for. So it was much more likely to find people that "had done it at all" (at least the parts they were genuinely interested in). 3.5, 4E and Next are not in this situation. So I wouldn't be surprised if Next is also replaced by a new edition 4-8 years after release.
Most people probably buy the new core rules. But even among the devoted fanboys, not all later supplements are bought. They get to specific, or the old books have hardly seen enough use yet.
So what can be done about it? Produce a new edition. Even if you still love the previous edition and have stuff unexplored there, this new edition may come with entirely new and interesting concepts. They are a breath of fresh air, and there is a perceived good reason to buy them even if your previous edition isn't "finished yet" for you.
3E may have had a unique situation - it did it after a really long running edition where not much new came out for. So it was much more likely to find people that "had done it at all" (at least the parts they were genuinely interested in). 3.5, 4E and Next are not in this situation. So I wouldn't be surprised if Next is also replaced by a new edition 4-8 years after release.