actually no one knows what the maximum value of bitcoin actually is, because bitcoin is elastic meaning it can go up and down. maybe we can see the price of bitcoin in the phase of increasing 100% from now on, even after experiencing a 100% increase we can't predict, because bitcoin can increase and decrease at any time. so it's hard to predict actually for bitcoin.
As much as we want to but no one really knows what will be maximum price that bitcoin can attain and we don't know also when it will happen. For me, I used to see bitcoin as a surprise gift each and every single day because I don't know what will be the next move of bitcoin price. It's unpredictable and every time I check the daily price update of bitcoin I've got surprised by what I've seen, sometimes its price dropped and sometimes it's just flying high. But one thing for sure I know that bitcoin will be more valuable than it is today.