But I think the edition treadmill is proving to be a failed model. At least the way wotc has handled edition transitions. They cant risk splitting the fanbase with each release of a new edition. They are a publisher and do need to sell books. I think the problem may be that they are expecting too much from such a small industry. They can certainly release new editions, but the first aim has to be retaining all the customers you currently have. How many more editions can they release before competitors eat up all their lapsed customers? This is why they are ven doing the "one edition to rule them all" thing in the first place. They are not the undisputed top dog anymore. And I think it is directly tied to their approach of cranking out new editions (It reminds me of the Gary Jackson board room meetings from knodt).
Yes, they are a business. Yes, businesses should try to make money. But angering your customers is a bad way to achieve that goal (especially in a small pool like the rpg community). I think a lot of people strongly dislike the new edition every four-five years (i know when 3.5 came out os soon after 3e, it really bothered me).
Oh, I'm not saying it's a good business model. I certainly have my complaints about every edition, and I (and my gaming group) even stopped playing one altogether. For now, however, that seems to be their modus operandi. Personally, I too have wondered at the increased pace of new editions. I long for those golden years where the expectation was for new settings, modules, and yes, even add-on rules as opposed to having to deal with a new system every 5 years.
I will say this: if the expectation is for 5e to truly be the uniter and not a divider (Oh, thank you GWB) then I would love to see WotC make a true commitment to that by publicly vowing to put out settings, modules, and adventures for... 7-10 years. That would say to me, at least, that they reallllly believed what they are portraying.