In 20 years, we'll be using gadgets that we cannot even imagine right away. I would be happy to hope that Bitcoin is going to stay one of them, but for some reason it seems to me that a better solution will be found on that time.
We also hope for best. I like your opinion is very good. Maybe in coming years, bitcoin will go up that not in history before !
If it has a good value I will sell it ofcourse. But you never know what will happen in the future and that is the problem.
But just hold your coins is very good. And just sell it when the value is very high and that will be good.