Whether it can be considered a bubble or not remains more of a philosophical question, but it is obvious that we will not observe the similar growth rate in bitcoin in the coming years.
first you need to make up your mind, it is either a bubble or a growth. it can not be both and it is pretty obvious which one it is. there is nothing "philosophical" about it!
Which brings the question about other opportunities to get this kind of return. I suppose these opportunities should be yet unknown to general public like bitcoin was in 2010.
that is the biggest mistake that people make and it is what keeps altcoin market mostly alive. people hope for a 2009 bitcoin to be repeated in an altcoin but they fail to use their brains!
the reason why bitcoin is rising is because it offers something useful. and because of that, the demand for it grows and with it the price rises too. sometimes it enters bubbles which are not as big as you think, they are small and they correct right after they are formed.
So in order to get this kind of excessive return we need to identify the next likely bubble, buy into it and wait until it becomes famous like the bitcoin. Do you think such instruments exist in blockchain world? Or you would bet on other tech sectors?
don't hold your breath.
if you want profit then just look for the altcoins that are getting hyped and then pumped. invest in them before or in the start of their pumps and get out of them just as fast.