The civil aviation industry likes to use what is proven and trustworthy, and will continue implementing designs that a are mature and safe. The design safety is 1 : 10$^9$ flight hour, and every time a change is made it takes a truly long time before the reliability and fault tolerance is proven.
So if 3000 PSI systems do the job on civil airliners, they will continue to be used in new design aeroplanes, unless there is a compelling reason to implement a fundamental change, which will result in deep R&D into applicability, reliability etc. Is there any fault condition that can impair passenger safety.
There is really old technology on board of civil airliners, for instance Intel 80186 and Motorola 68020 processors are still being mounted in new aircraft. A ripe old processor design sold 30 years ago, the stone age of the digital era.
Military aircraft are different. Safety is not the overriding factor, but mission capability is. Yes the pilot must be brought home if the plane comes down, but above all it must do its job competitively. So in military aircraft there is a drive towards modernisation, while in civil aviation there is a drive to not change anything that is working reliably, unless a specific problem must be solved.
3000 PSI was what the first hydraulic systems used for operating pressure, the initial hiccups were fixed, and there it remained - until there came an aircraft that was so huge that the line losses simply became too big. It had to be done. Fortunately the system parts for 5,000 PSI were already available, from the military suppliers. That is where a lot of new designs mature.