I remember when people thought a 50" TV was big, and that wasn't all that long ago (~2008).
Uh, 40" to 50" sets were common even a decade ago. They just sucked because they were rear projection sets.
70" now, is the old 50"/60". People aren't buying 70" sets because they can't accommodate it in their homes, it's because they can't afford one. Trust me, once 70" sets come down in price, it will become the next standard in TV size.
I won't buy ever a 70" set for my living room because I think they're monstrous and awkward. I'd consider buying a 90" set for my home theatre room if my projector dies, but I won't pay more than $2000 for it.
You must have a fuzzy memory. People back then proclaimed BD was a new gimmick the studios were trying to force on them. There were several discussions on how BD wouldn't be successful because "streaming media was the future" or that they couldn't see the difference between DVD and BD.
These were geek discussions, not fighting from consumers. The point here is that consumers will buy if products are cheap and make sense. 3D makes no sense. 4K to target 70" TV is neither cheap nor does it make a huge amount sense any time time soon for many reasons, including smaller TVs (popular in most homes) not needing it at all, cost being too high for the big TVs (for the near and mid-term), and even stuff like network infrastructure concerns.
Meanwhile disc rental places are dying left and right. I can't even rent a Blu-ray disc locally anymore because online rentals are taking over. All my local movie rental shops have gone out of business.
Blah, blah, blah. Well, it was successful and the same will be for 4K.
You missed the part that DVD still dominates, and Blu-ray is much less popular. Players are popular because they are only $79.99, but people still use them mostly to play DVDs, or watch Netflix, or even to watch bootlegged MKVs.
I think of 4K as the new 1080p. In the past it was 720p vs 1080p and if 1080p was really worth the extra cost. The same will be with 4K. Lower end sets will be 1080p, while the high end sets will be 4K. If consumers don't want to pony up for the extra quality that 4K provides, they can stick with the "older" 1080p sets. Me personally, I won't upgrade to a larger set (70"+) unless it is 4K.
I think of 4K as "beyond 1080p". 480p was great for the time, but even then the detail was lacking enough for even common consumers to sometimes notice on those larger rear projection sets. Not so with 1080p and LCD/LED/plasma. People don't complain about video resolution any more. Yes 4K is better, but people aren't clamouring for it. I'm certainly not. I'd buy it if the price is right, but only if it was a mild price premium and my existing TV died.
I can't speak for Europe, but in the US, bigger is better. And 70" sets are pretty easy sells if the price is right.
If the price is right. As I said earlier, don't expect any meaningful 4K adoption in the near or even mid term. ie. 2020. After that all bets are off.
I do expect 4K to be eventually available in mainstream TVs, but I don't expect it to be major selling point for most people, just like 3D is not a major selling point for most people.