Don't confuse the chatterings online about RPi etc with any kind of general movement. The vast majority of computer users now use sealed hardware boxes, and that proportion is increasing.
As long as our software is continually developed and is supported (which is why UEFI is so scary), I don't see why we should object to black box computers.
Do you think this is an entirely new development? Wouldn't the statement "5 years ago people could do X with computers, now they can't" in fact hold true for the last, say, 40 years in the history of computing?
Computers in the olden days tend not to be hermetically sealed black boxes.
One way I can think of is memristors, which could make FPGA-like hardware ubiquitous. This would push the software/hardware frontier so low that there would be effectively little magic left.