That said, would it be worth it? Sure, over a period of several years they could gradually bring classic books back into print or create usable PDFs for them and sell them. And I think they would make money. Not megabucks, no, but a steady income stream over time. In the long run it would pay off.
There is an entire segment of the RPG market that caters to fans of legacy editions of D&D. The most popular products in that market generally sell several hundred copies over their lifetime. Taking resources away from making products for the current edition of D&D in order to generate the trickle of profit they would get from investing in legacy D&D would be one of the worst decisions WotC could possibly make.
It's not a question of whether engaging that market would generate a profit (let's say for the sake of argument that it would). It's a question of whether that profit would in any way compare to the profit WotC could generate investing the same amount of resources and man/hours in working on the current edition. It would be akin to a dentist working half time at his practice so that he could operate a lemonade stand in his front yard in the afternoons. Yeah, the lemonade might bring in a whopping profit of 10 cents/glass (clearly, a steady profit stream), but he can't possibly sell enough glasses of lemonade to make up for the $100-200/hour profit he is losing by choosing not to be a dentist for several hours a day.
