Can the top 10 or 20 coins disapeare?
Actually yes, the list of top tokens is also changing with time. What we can be really sure about is that Bitcoin and Ethereum must always be at the top. Other currencies are likely to become less popular. I remember that the top-10 was completely different some years ago. I saw Ripple, Ethereum classic, Litecoin there, but now their places are replaced by BNB, Solana and Cardano.
The top 10 positions change every year because many new or old projects are trying to develop their projects better. Sometimes, the new position can surprise us because we do not predict that the coin/token can replace the old coin/token already got a good position. This year, that position already changed and every coin/token still competes, so I think the position can change again at the end of this year. Solana is now trying to increase more and attract more investors so it could have a chance to lift its position.