There's no guarantee that btc price will go up in the next 10 years. In fact, it can go down to pennies. Remember, what goes up, must come down.
if you look at the all-time chart you can see that bitcoin is actually rising(average rising) every day by a few cent, if this trend continue, bitcoin is aiming at going up and not certainly down
most people don't see that as they are mostly focussed on the very short term. they are interested in instant profits only. not in the long term picture.