Everyone saying the altcoin market will make the same percentage gains as 2017-2018 bull run is not looking at this with a realistic view I think. We're not going to a 100 trillion USD market cap for altcoins this year, and not in the next 4-5 years either.
Example: BTC is not increasing with the same % every year. The percentage decreases over time as the market grows.
A 2x increase is possible at the minimum. If BTC gains a lot, then there is more potential for the alts of course.
Some alts will do way better than other alts of course!
Coins like ADA will certainly have the potential to "moon" another 10X; sure.