To me this is the entire meat of the question about 4th edition.
The goal of WOTC is to try and get the gamer to buy a print version of the book, subscribe to the online D&D insider, and enter the codes of the books that you have bought to unlock electronic version of the products. Being able to have the clarifications from the equivalent of Sage Advice immediately incorporated into the core product to correct problems would be a good benefit. This isn't any different than reading the print magazine and incorporating clarifications and corrections into your table game.
Why I chose the above quote is that this electronic model does not easily support customization. If we really look at all of the great electronic D&D support products that are out there, how easy is it to support customization to allow you, the consumer, to put your favorite rules into their character generator? Will WOTC be motivated to do this in D&D insider tools? What are the legal ramifications of incorporating the (pick your favorite company's name and insert it here) rules/classes/monsters/skills/etc. into the D&D insider web site tools?
The real criticism of this model is that when you play through the D&D Insider site or use those tools, I suspect that it will be difficult to incorporate homebrew or OGL stuff. Bringing electronic support into the 4th edition may effectively undermine the OGL unless the publishers give up product identity claims and allow their content to be merged with the WOTC content (assuming WOTC is willing to incorporate any other companies' content into their site and tools).
I think that the fear that the other D20 companies will go off and make version 3.75 to compete with 4.0 is unfounded. I think instead that the publishers should be worried about how they are going to capture any of the new audience that WOTC is trying to attract, since they won't necessarily be able to offer integrated electronic support.
If you are a GM or player that likes products from other D20 publishers, maybe you have been fired.