The trains of the future are almost always trains of the past. Everything has been tried for a very long time.
"Hyperloop" is a compressed air train inside a tube ... It has already been tested between London and Sydenham since the 1850s with a conventional train in the form of a piston which was pushed into a tunnel by Compressed air and which, once out of the work, was traveling about twenty kilometers on its wander ...
Magnetic suspension trains? There, too, tests were carried out in 1913 with the French Bachelet system.
As for the pendulum train, it rolled in 1938 in the United States. And if we take the example of electric locomotives, we could find them as early as 1840, tried with electromagnets wedged on wooden drums.
Hyperloop is not a compressed air train. The model you describe did not create a near vacuum in the tunnel, just created a pressure differential between the front and back of the train to move it, like those pneumatic capsule tubes in banks.
Hyperloop trains are not pushed along by an excess of air pressure behind them, but instead propel themselves electrically using ducted fans. Some of that air is used to create an air cushion under the train which, in conjunction with electromagnets, levitates it off the track slightly.
By traveling in a near-vacuum, wind resistance is all but eliminated, making much greater top speeds possible. The only similarity between Hyperloop and the train you mention is that both travel inside of tubes.