Given that D&D involves planning a character for the future, "constant updating" isn't necessarily a good thing. The other problem with subscriptions (for a consumer) is that you're paying for something before you get it. I do not buy D&D books (or most things) without thoroughly evaluating them first. It puts pressure on a company to constantly produce a high volume of quality products, while a subscription model encourages them to do things to attract subscribers, who will then likely remain subscribers even if they are later charged a higher price or given lower quality (or quantity of) material.
The OGL has simply raised the standard, making it more difficult for rpg companies. I now expect free, high-quality material to be available online at any time in a user-friendly format. I expect to pay money only for something that I have already determined is worth buying due to its usefulness at the table. This is how 3.X worked (and now PF, which releases most of its stuff open and still sells books pretty well). Similarly, I would quit watching anything on Hulu if they charged for it (regardless of how much), and I would not watch the same material in other formats. When I can have free, quality, material in any arena, why would I settle for less? Subscriptions are less, because nothing is free.
Subscriptions are good for some things, but not for rpgs. Keep in mind that I was never saying that the edition cycle was great, I was saying that rpgs are a young hobby and that the ideal business model for them (if such a thing even exists) has not yet been found.
I'd say you missed the point. Without a subscription model, you'd get no Adventure Paths from Pathfinder. An AP would cost WAY too much money for Paizo to put it out in a traditional format. The online tools in the DDI cannot exist side by side with the OGL for exactly the reason you state:
If you put OGL in an electronic format, someone else can simply copy what you've done and present it for free. The tool isn't the value, the information that the tool accesses is. If the information is 100% free, then the tool will never make any money.
There's a reason Itunes makes buckets of money. If copyright didn't exist, Itunes would vanish in an instant. But, because of copyright, information is not free, and Itunes can flourish. Itunes itself isn't worth anything.
DDI, in and of itself, isn't really worth anything. But, the information that it accesses in the format that it does, is judged as being of value.
I think most people who subscribe to something like the DDI or Pathfinder realize that a large amount of the information they get will not be of much value. But, the information that is used is judged as being worth enough to justify the payments.
The traditional model of continuously selling books to smaller and smaller markets just won't survive. This isn't just RPG gaming. EVERY book publisher is facing the same thing. There's a reason that Asimov's, for example, is now an online magazine. Traditional delivery models are complicated and complicated is expensive.
Given the size of the industry, expecting a traditional model is unrealistic. When book publishers are going more and more to online sub models - Marvel Comics? DC comics? (both of which are a HELL of a lot bigger than RPG gaming) - it's totally unrealistic to expect that RPG's will be able to carry on as if it's still 1987.
You might be able to get away with it if you go with the luxury model, such as someone like Subterranean Press does. But, are you willing to spend $140 dollars on a single RPG book?