Wow, where to begin???
First of all, nobody has ever said that Facetime was "the main feature" of iOS4. Nobody at Apple, nobody in the blogosphere, really, just you at this point. One could argue that multitasking was the "main" feature, but even then, you'd be forgetting the other six of the seven "tent poles " of iOS4.
Next, what exactly does Facetime really do for Apple? They don't make any money off of it, it works over WiFi only, and in it's current incarnation it only works with iPhone 4, needing a telephone number to be initiated as it's ID, so to speak. Unless the new iPod Touch is getting 3G (not likely) then it's out of the picture along with the millions of 3GS phones out there without a front facing camera or the internals to support the feature. How many of those 1.7 million people who bought an iP4 did it for Facetime, anyway? I certainly didn't, and I would guess that I'm not alone.
Finally, like so many others have said here, why on earth would a company who can't make enough of the current model to meet demand slit their own throat and jump the gun with a six month refresh window on the hottest selling product they ever came up with? It would be one of the most idiotic business decisions they could make, and as a stockholder, I would be demanding the head on a plate of the fool who thought that was the way to make money long or short term. Have you ever heard the phrase, "If it ain't broke, don't fix it"? You need to think more like a businessman and less like a user on this one, no offense...
The iPad is a runaway freight train of sales right now, with long wait times at all retail outlets and from apple.com with premium prices still being commanded on eBay, etc. There is a small percentage of hardcore Internet geeks who demand more out of it, but 3,000,000 and counting are loving every second of their first gen iPad.
Holding up the iPhone's original launch issues does not apply. It was priced wrong out of the gate, sales were not nearly as brisk, and Apple made adjustments sooner than later to correct their course. Not gonna happen this time around, so look for iPad 2 in the spring of next year.