In a previous life, I've flown the IL-86 with Aeroflot in the early 90's to Moscow. The business class in the front was packed full, but we were maybe 40 passengers in the back to share about 270+ seats.
That was my first flat bed experience ^

Seriously, as aircraft designer (which I do for a living) I have no boubt we will see it in our lifetime. There are concept aircraft that I can see 20-30 years away, that are going to be much slower (think Atlantic in 12-16 hours) but absolutely huge inside with choices of entertainement and privacy.

With the current type of airliners, it does not make economical sense.

The equation is easy, squeeze in your seat and go fast, or enjoy your trip and go slow. There will be offerings across that spectrum, but it will be awhile.