Apple has had iPhone supply issues (3.5 screen).
Apple had iPad supply issues when it came out.
Supply issues was the only negative point in the earnings call Q&A with the folks asking the questions.
I don't think Apple would want a situation where they really constrain supply by including a screen that the industry can't supply them in bulk. They are having these things being grabbed out of their hand. From a business point of view there isn't any reason to go above and beyond.
You might keep repeating Xoom and whatever else, but I read the same thing over and over about HP Slate, and look at where it is. I think vapor is the right word. No amazing sales of "S Pad" (not the sales to retail numbers Samsung has released), and Norton Ink Adam... well, we'll see how they are once somebody actually gets their hands on one.
You guys keep bringing up iPhone 4, but it took Apple 2 years of mediocre product iterations (3G, 3GS) before coming up with the 4. They are certainly not the goose that always ***** golden eggs.