Technologies may become obsolete with the advent of other technologies or social changes. I think Bruno Latour makes an important point here in stressing that human and non-human (technologies) should be thought of as one. So, a technological change might go hand in hand with a social one. I don't think it has to be a disaster though.
This isn't really an undo but rather the result of some pruning when an obsolete tech isn't economically viable any more.
I'm inclined to think this is true, but on the other hand, survivorship bias...
It won't be long before smartphones are in our heads.
Yeah, that's worse, not better.
I suppose technology can go backwards, but only by way of generation-spanning disaster. The fall of Rome is an obvious example. I guess this means we'll be dealing with this constant technological overload for the rest of our natural lives, huh?