Here is my undeveloped take. Presently if there is a fork, the IRS considers the new token to be an income event. My belief is that the new token would have the same value as the old token at the time of the fork which means if its 100k and you have 1btc, youd have an income event of 100k due to the creation of 1newbtc and would have to immediately liquidate the token to pay taxes on that income event which would cause newbtc price to crash immediately. This is assuming no pre-fork legislation conspiracy to exempt the newbtc from such tax treatment.