Also, the number of units a coin has does not relate to market cap: that's not how math works 
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.The market cap is the number of coins in circulation multiplied by the current price so the number of coins in circulation definitely has a role. You see coins like Shiba inu with 0.000018 as price per coin among the top 15 coins in the market based on market cap simply because they have over 580 trillion coins in circulation.
I believe the overall market for digital currencies will be 10x what it is today in ten years, but a majority of that growth will be non-Bitcoin (and non-blockchain, imho) currencies.
I understand what you mean and you might probably be right, but 10x more in 10 years is a big reach. I don't see that happening. Maybe I'm being a little pessimistic, but it's hard not to be based on this prediction. I know the altcoin market is growing rapidly but I doubt it will grow that much in the next ten years.