Is Ethereum going to grow as big as Bitcoin by 2022? 
look at the circulating supply of ETH and BTC, nearly 6x.
If ETH catches BTC its volume should be nearly 6x higher than BTC.
It can happen IF ethereum is highly scalable with low txn fees,but there could be another new tech that will surpass the ETH and BTC.
Stay addicted to crypto and DYOR,You will find the next bitcoin or ETH, if theses assets fails in future.
Anything can happen.
There are lots of platforms coming out,One of those can be the 1 or a future project will win.