Two of the major changes weren't new. Standardization and character customization were, by 2000, old innovations in the roleplaying game hobby. D&D was long overdue to add a little dose of these improvements in game design since Gary Gygax pioneered the industry in 1974. By the time we got to 4th edition, Wizards of the Coast had amped up the standardization aspect while dialing back the level of customization in an attempt to make the game understandable by designers (so they could balance game mechanics against each other).
One truly visionary innovation came out of WotC's relaunch of the flagship game in the hobby industry: use with the Open Gaming License. It took a lot of courage to champion the OGL concept within the halls of Wizards of the Coast. It is easy to understand why the underdogs would band together to create a virtual game that was bigger than any of their individual products.
Does Hasbro benefit from allowing the OGL to apply to D&D?
I am a proponent of centering your business on your customers. The argument goes thusly, if you give customers something they truly value then they'll reward you for the benefits they've received. Just to illustrate the contrast, an opposing perception is that you can "sell" something to consumers and convince them to want it. While I don't subscribe to "creating demand", the theory does have a tiny element of truth inside it in that sometimes people don't know that they'll enjoy something until after they understand it (which generally requires them to give it a try). Back to my point. If the players of Dungeons & Dragons benefit from an OGL for D&D then that should increase the probability people will play the game. More players leads to higher sales and revenue for Wizards of the Coast, a division of Hasbro, Inc.
You may have noticed that I hand-waved some of the details in order to get to the point. Ryan Dancey suggested that, through the d20 System OGL, Wizards of the Coast would benefit from "network externalities". When everyone, or almost everyone, uses the same rules engine it is very easy for players to move around within that system. Further, it would be less likely that anyone would leave the d20 arena, it would be more likely that new players would try the d20 system, and ultimately it is the most powerful force within d20 gaming that benefits the most from this arrangement. When the d20 System logo was used, D&D benefited directly because a Player's Handbook and Dungeon Master's Guide were necessary to run the game.
Wizards of the Coast cannot, and in some cases will not, satisfy every niche gamer demand. The size of the beast (sorry, Wizards) is such that a certain minimum sales numbers are necessary to make a profit and that threshold is higher for Wizards of the Coast than for leaner operations like Green Ronin (or vanity publishers). For example, take D&D Next and the wizard character class; some people are interested in highly powerful magic-users that are balanced by their fragility as we see in AD&D 1st edition rules. An OGL for 5th edition would allow someone to satisfy this minority demand and thus keep those players interested in D&D Next. This would be a boon to the "unity" goal of the upcoming edition.
Game publishing is a mix of game design and game development. Design being the Mark Rosewater activity of exploring "new" game space and development being the Aaron Forsythe* activity of perfecting "existing" game designs. Sometimes exploration leaves you empty-handed and you end up with a failure. Allowing other individual designers and companies to play in the D&D rules sandbox allows Wizards of the Coast a huge amount of free design resources. Dungeons & Dragons R&D can produce their own innovations while they simultaneously watch for ideas within the industry that work. Any movement forward in game design on behalf of D&D is something that Wizards R&D can leverage internally.
The players of the game are the true winners. That's good for D&D and its owners.
* Yes, I know that Mr. Forsythe has been promoted from head of development so that he is now the head of all Magic: The Gathering R&D including both design and development aspects of the product.