Is there a situation where we woke up one day and found out all our bitcoins vanished? Blockchain or DLT has a common explanation where it is calculated to solve double spending problem which represent a incomparable transaction that are solve through the computers in the network?
Don't think that in the future it will never happen let alone Bitcoin, humans can disappear/die as you asked, what's more bitcoin that is run through the internet network, there is no guarantee that the internet network will remain intact forever.
For that my advice is that you don't think too much about Bitcoin that you don't know about, now what you see and know is the best and what you can do, you want to invest, trade and so on, that's the best thought for you to do, don't fantasize about tomorrow, the day after tomorrow and so on Bitcoin is like this and that, remember: if we know what will happen in the future, of course we don't want to do anything but good, we are currently living in this world, not in the hereafter.