Uh, 40" to 50" sets were common even a decade ago. They just sucked because they were rear projection sets.
Again, these sets were considered "big" back then. They aren't now. Just about any Joe has a 50" set now.
As for the rest of your comments, I'm not going to go quote by quote, instead I'll answer them all in one post. Whether you want to face it or not, people ARE looking for larger sets. One of the biggest questions that comes out of the plasma camp is, "when are we going to get a 70" plasma?" Currently Panasonic and Samsung offer the largest plasmas (practically speaking) coming in at 65" and 64". They sell VERY well, and you're going to tell me people wouldn't be interested in a display just 5" larger with a much better resolution? You either are just speaking for yourself, or you are seriously underestimating the market.
As for BD battles, yes they were geeks battles, but outside of that, the general public didn't even know what BD was, let alone care enough to spend big money to overhaul their existing setup. But like with any new tech, the early adopters pave the way for the average Joe Blow, as will be the case with 4K. The videophile early adopters will get the latest and greatest first, while others pretend it is no big deal until they can afford it. Then it becomes the best thing since slice bread.
And in regards to DVD vs BD, DVD was in a different era than BD. DVD didn't have to compete with streaming content, torrents, and didn't require a different TV. That being said, just because DVD sold more in the past, doesn't mean Blu-ray is not a success. It definitely is a success, but it could have been better.
But let's get back to 4K. For me, if they can get a 70"+ 4K set out for under $10K before 2015, I'll jump all over it. And if they can offer an 80"+ 4K for under $10K, I'd be ecstatic! Everyone else can sit on the sidelines and pretend 1080p is good enough.