They’re going away in general as airlines look to save weight and slim seatbacks, and recognise that the vast majority of people have a portable entertainment device with them.
That may have been a brief trend on domestic flights with older airframes, but that isn't the general aviation trend. The last thing you want is more lithium batteries charging and discharging on a long flight over the ocean.
This doesn’t make much sense. If there’s an explosive risk, then it’s going to be a huge risk over land as well, and it doesn’t make sense that they’d be increasingly putting outlets at every seat.
The WiFi on planes is satellite and something like 256 Kbps with extreme latency. It works fine for light web browsing and email, but it's unusable for video streaming. Your options are to pre-load entertainment or watch what the plane has pre-loaded in the seat-back entertainment screens.
I hope not. I fly Delta specifically because I can watch new release movies and other entertainment on board. It's amazing for those cross country flights. I hate flying United which has no such option.
I love flying United (or Jetblue or Alaska), they usually have access to Amazon Prime movies for free. And they tend to have plug outlets and chargers at all the seats.