You are looking at it backwards. In the continual race to the bottom, TV manufacturers removed quality speakers and they are now being sold separately as soundbars. People don't want soundbars as much as they need them to provide the audio that should have been included in the TV in the first place.
Because more than 90% of people want speakers with their TV. And having them attach on is always worse than having them be built in from an engineering/reliability standpoint.
The ascendancy of sound bars may begin to change the portion of people who demand speakers, but the idea they won't be built in anytime soon is pretty much wishful thinking on the part of a small, small minority.
Bingo. Rogo gets it once again.
Many people on avsforum have outright contempt for people who use the speakers on the TV. One of the reasons I selected a Sony XBR5 over the Kuro is that the Kuro's speakers looked like the detachable devices they were. Do the Sony's speakers match a 5.1 or 7.1 system? Nope. Do I care about watching football, golf or most tv programs in 5.1 or 7.1? Nope. Do I want to watch loud explosions when my daughters are sleeping? Nope. So I use headphones. Do I want to be able to actually hear dialogue? You betcha. And a good pair of speakers on the tv fits the bill quite nicely.
Surround sound setups are also not well suited to family rooms in the open floor plans found in most new construction.
As it relates to OLED, I'm very concerned that in order to make them thin, the speakers will be terrible or removed altogether.