if someone holds 1btc from 2015 till date, how many btc will the person will be holding currently base on current Bitcoin values
Is it a valid question?
If the person held 1 bitcoin since 2015, he has 1 bitcoin since that year or did you speculate that since 2015 whether he has accumulated more bitcoins?
There is no way to identify bitcoins held by one person and we only can identify Bitcoin addresses with + balance.
https://www.coinglass.com/pro/i/hodl-waves-supplyThis is the same issue of unable to identify whether inactive UTXOs are from people who lost their bitcoins or just holding.