You are counting altcoins too, which is in my opinion not very correct, because it's very easy to create millions of marketcap "value" by launching new coin (or just ERC20 token) and trading it on exchange. Also, Bitcoin is the main cryptocurrency, and value of all altcoins is pegged to it automatically, because they are mostly traded against it, instead of fiat. And this 90-100 billion range is actually quite small if you compare it with classical assets, or even just marketcap of Apple, so there is a lot of space to grow. Basically, Bitcoin will either grow 10-20 times in next 5-10 years, or will crash for some reason. This is why it's better to just hodl if you are not an expert trader.