I see no reason to believe that the RPG market is similar to the toothpaste market. You need to buy toothpaste regularly when it runs out, and you can count on brand attachment. You do not need to buy RPG products regularly, and they are not widely considered a necessity.
Crest having 17 kinds of toothpaste allows it to compete better with other brands - it helps with shelf space, ad campaigns, etc, and their market is literally every person in the country.
This does not hold true for RPGs.
-O
All true. However, RPGs are not exclusive, typically. A gamer doesn't usually have such brand loyalty that they only buy one--and only one--game. There are collectors who buy whatever they can of games they like without ever playing them. There are gamers dedicated to fantasy who buy anything that looks good. And this doesn't apply to just D&D, but all games. Buying the 5E PHB does not preclude you from buying any other PHB ever. People are introduced to games before they buy them, if it's fun, they pick up a book or two.
Look over at the poll about people switching to 5E. All those customers--all those sales--just sitting there, waiting for WotC to sell them a product they want, which WotC owns the rights to. Despite all the faults people seem to find with the blog quoted up top, it was perfectly correct when it said you can't make people buy something they don't want, and it's really damned hard to convince people they want something. Especially those people who have resisted that same call of a shiny new edition several times over.
People already have all the older editions that they like. The people who won't switch, won't switch. Those who will switch, will. The people holding on to their older stuff and staying put aren't going to be swayed easily, if at all. But, all those people are potential sales of new copies of those older editions. This is a simple fact that is being overlooked.
People will switch or not switch to 5E for their own reasons. Other than making a great edition or a crappy edition, WotC can't really do a damned thing about it. The old line of Wizards coming to your house and stealing your books comes to mind. If they'd rather play older stuff they're going to despite what WotC does. But, what WotC can do is sell them what they want.
They don't have to actively support each edition, but they can sell edition neutral materials, like setting material. Right now people play 2E Forgotten Realms and WotC makes bupkis. If WotC re-released 2E core books and 2E Forgotten Realms setting material, those are all potential sales.
Look at those poll numbers again. After 30 years of being tempted by a long chain of new shiny stuff, some people are simply staying put. That's a fact. And each one of those people are competing for a dwindling supply of paper books long out of print. WotC would be stupid not to try to capitalize on their catalog. How many users does Dragonsfoot have? Almost 8000. Each one a fan of pre-WotC material. Some play WotC D&D, sure. But how many? Each one of those is a customer WotC is throwing away. It really is a ridiculous business model.