Unfaithfulness to the customer? As in, their current/past customers?
If you're a customer and are purchasing 4E books, it is almost a given that you already have the 3 core rule books.
I don't see how not being able to re-buy a book that you already have is somehow unfaithful. If anything, WotC have been entirely faithful to their previous customers by providing errata for free online rather than only releasing it through reprinted books.
Your books are still compatible with the game and no-one is going to take them from you - this only impacts future new players who might want to go back and find the older classes without using the DDI.
Yeah, yeah, I know. I still have the books, and the WotC gestapo won't come take them from me. The fact of the matter is that they promised there would not be a 4.5. If the Big Three are going away for any reason except to be re-released as revised editions, then we've either got 4.5 or a new edition, regardless of what the marketing folks want to call it. 2 years. That's all we got off of 4E. If this is true, that is.
I love 4E. Every game that my group plays that's NOT 4E makes us want to go back to it. Every book that comes out we anxiously await. We can hardly contain ourselves waiting for the Dark Sun 4E books. I have no desire to play the watered down version of it that Essentials appears to be. I'm no WotC hater. I've spent more thousands of dollars than I care to think about on 2E, 3.xE, and 4E. I've been well-pleased with most of the changes that the line has gone through over the years and have gladly spent money on most every book in the lines from 3.xE to 4E. This isn't about being "forced" to buy new books. This is about support.
If you are worried about ongoing support for 4E as a system, it does not appear that the 4E system is going away. In any case, the 4E system is more than the PH, DMG and MM.
True, I don't need more books. But it has to do with the expectations that Wizards has set. All versions of D&D prior to this have lasted several years, with numerous supplements that followed. When I buy the PHB, it's with the understanding that it's a gateway to the products that were going to follow.
1E got 12 years. 2E got 11 years. 3E got 3 years, and then 3.5 got another 5. The implication of the claim that there would be no 4.5 is that there would be several years of this edition. Did anyone but the most cynical seriously consider 2 years ago that we'd be talking about the Big Three no longer being published now?
I sometimes think that gamers generally expect more from gaming companies than most ordinary people do from regular businesses. And I really wonder why.
If WotC had come out and said that 4E would be a 2 year product line to explore the ruleset before moving on to other things we wouldn't be having this conversation. Those who bought in would know what they were getting into. That is, apparently, not what we have here.
I expect tremendous quality from brands that I support this fanatically. I go to my favorite restaurant all the time because of the food quality and the service. I buy every UFC pay-per-view event because they put out a quality show time after time, and are pretty darn honest with the public about their dealings. I buy my favorite authors' new books sight unseen because of the quality of the writing. I expect consistency and honesty from these brands, and I don't think I'm alone in this. When massive changes come along I expect to be informed, and not have to guess and deal with corporate doublespeak.
If WotC wants me to expect from them only what I expect from "regular" businesses, then in return they'll receive the same brand loyalty I have for those "regular" businesses, which is, essentially, none.
EDIT: If all of this proves to be false, and the Essentials line really does coexist as a starter set, then all will be right as rain. But honestly, the marketing for Essentials has been abysmal. In their hopes that Essentials would be purchased by current players, lapsed players, and new players alike, they've given very little information as to what Essentials IS, and what it MEANS to 4E as a whole, and have laid the groundwork for this whole mess of speculation.