I wasn't necessarily suggesting science as a test - just that if you are making an objective claim (god/'the supernatural' exists in some objective, 'true for everyone' sense), then you need an objective means of testing that claim.
Either the supernatural (i.e other than natural) exists or it doesn't. But within the constraints of language and any other tools currently available to me I have no way of proving it exists or falsifying it in the way you mean.
I think that is the point - since it is called "faith". Faith - a subjective term - is different from knowing in the objective sense. When people no longer have any use for "faith", presumably the word will become archaic, obsolete and people will want to only operate on the basis of what they can objectively show.
We don't "know" if faith becoming obsolete will happen at some point in the future - you can hold the opinion it is likely, you can believe that this will happen, you can even have faith in it happening if you want and operate your life on the basis that it will happen. Maybe because you detect certain patterns of behaviour or vibes from people you talk to that this is what will happen eventually. But if you are asked right now whether you know this will happen - you don't know and there is no way of currently testing for it to objectively prove that this is where humans are heading.
There isn't anything wrong with not knowing something. However, if you don't know if god or 'the supernatural' exists, then what is the point of having faith that they do?
In fact, if there isn't any hint of any objective evidence for these things, then it seems to me to be irrational to believe that they are objective realities.
Humans have believed in a vast number of gods, not to mention many other 'magical' or 'supernatural' beings and practices - all of which have exactly the same amount of objective evidence to support them (none), so why would anyone have 'faith' in one out of them all?
I think having faith in something is usually a work in progress, an on-going process of questioning, thinking, developing different perspectives, it gets you thinking, wondering.
I could just have long, philosophical, emotionally satisfying discussions without introducing the supernatural into it, but I did that when I was an atheist, and then I got interested in having long, philosophical, emotionally satisfying discussions with a supernatural element to it. But if you ask theists there will probably be lots of different reasons for their faith. I just highlighted one reason off the top of my head. I am sure if I think about it I will have others - but this isn't really the place to get too personal. People aren't interested in the why, it's more a place to try and win an argument.