The term "hypersonic" is not a particularly helpful one. The generic term refers to an missile system traveling faster than Mach 5, but there are 3 distinct types of weapons that fall into this category, which are very different.
1. Ballistic missiles: most ballistic missile systems are hypersonic. We've had ballistic missiles since WW2, the very first American ballistic missile (the redstone) was hypersonic, and that was back in the 1950s. This is not new. People make a lot of missile like the Khinzal, but this is just an air-launched version of the Iskander missile, which is from the 1990s.
2. Hypersonic glide vehicles: normal ballistic missiles drop a re-entry vehicle that just falls to earth. It might have some stabilizing fins, and some ability to make minute adjustments to its course to improve accuracy, but this is limited. In a hypersonic glide vehicle, the re-entry vehicle is meant to be more of a glide body, and is able to make actual maneuvers and turns. The technology here is also not new. For example, the Space Shuttle is an example of a hypersonic glide body. Research in this field has been around for a long time, though it's only in the last few years that countries have begun actually fielding weapons featuring glide vehicles. The annoying part with this is that the term "hypersonic glide vehicle" implies that the reason these are so difficult to intercept is because of their speed. But it's actually the opposite: in order to maneuver, a hypersonic glide vehicle actually has to travel slower than a traditional ballistic re-entry vehicle! The advantage of a HGV is not its speed, but its ability to maneuver, which makes it harder to intercept.
3. There are also hypersonic cruise missiles. These are missiles that use ramjet or scramjet engines to fly at hypersonic speeds. These tend to be even slower than HGVs, and will have much shorter ranges because they have to consume fuel to maintain this speed. Several of these are in development, but I don't believe any have been fielded. The main advantage of these is even further maneuverability, and a lower flight altitude which should make them harder to detect. Additionally, because they are flying in the atmosphere, it requires a different type of interceptor to defeat.