It's hard to look very far in the future but one thing is for sure, electronic devices are getting smaller, more powerful, and cheaper. The technology is changing so fast that many things are out of date before they make production. Look at computers in the last 30 years. Remember 8" floppy drives? Punch cards? Magnetic tape? Terminal programs? C:/DOS?
If metal detecting technology progresses at a similar pace, in 20 or so years you will have a small machine that sees under the ground. It shows you what is there in 3-D color. Don't like the stones in the ring, just hunt a little longer until you find the stones you like. See that dime by the pull tab? Ah, it just a 1960 I think I will leave it but that $5 gold piece 3" underneath I think I'll dig. Impossible, no way. Will it happen? Don't know. But if it happens, metal detecting as we know it is dead and you CAN go to an old park and clean out every coin and leave everything else.
Don't get discouraged now by not finding good coins. Like they say - coins is coins. Take the clad when you can get it. If you don't like the coins you are finding, I would suggest three things. One is to make sure you and your metal detector are operating at their peak level of performance - know your signals, know how to discriminate, use your test bed. Just make sure you know your machine and it is working at max. Two is to research the area you can search and locate some spots that have a better chance at having better coins. Try to get on some land that has not been hunted like farms and private residences. Three try out a different metal detector and see if that may be part of the problem. Your detector can be a quality detector but your ears and brain don't work well with what it has to offer. It happens. Hearing and interpreting sounds is different for different people. You could just be a mismatch for your detector.
Hopefully you will start to find better coins. For me, I still like finding the clad The thrill of getting a good signal and an unknown target to dig does it for me. That's all I need.
Daryl