In 1968 you looked back 50 years to 1918 and realized how much incredible change took place. Extrapolate out 50 years and the future probably looked close to the movie 2001: A Space Odyssey, released in 1968 Any chance we can get that future?
Many future predictions from the 1950s were based on the promise of unlimited electricity. Once this comes to pass, we can have hovercars and whatnot. Instead, we got "unlimited" information. Although this doesn't translate as well into physical products, the world still looks/feels wildly futuristic if you orient your perspective correctly.
Some 1968 futurology predictions seem like they might have come to pass had energy remained as relatively cheap as it was in 1968. Others of them were frankly ridiculous regardless of the price of energy. According to the Amazon review, disintegrator rays and anti-gravity belts were a couple of the predicted developments from "Toward the Year 2018." There was no scientific phenomenon known in 1968 by which either of these could be implemented. It's like the predictors reasoned "science fiction was prescient in predicting artificial satellites and travel to the moon, therefore its other popular tropes will eventually come to pass too."
There's a lot still to explain about the universe: dark matter, baryon asymmetry, dark energy... But I'm not convinced that new insights into these problems, if/when they arrive, will unlock significant new technological capabilities, any more than the discovery of neutron stars led to new superhard/superdense materials for human use. I think it's quite likely that humans never tame a more energetic primary energy source than nuclear fusion[1], nor send messages or vessels faster than light, nor manipulate gravity with the facility that we manipulate the electromagnetic spectrum. The engineering permitted by classical and quantum mechanics, modulo additional limits imposed by relativity, is vast. But it can't deliver everything that science fiction imagines. Inertial compensators, gravity manipulation, tractor beams, teleporters, disintegration rays, time travel, FTL: nope, probably not.
[1] Storage and use of antimatter for compact power sources seems like it may be eventually plausible, but it would function more as a super-energetic "battery" charged by other primary energy sources.