Earlier quoted context omitted.
You don’t disclose assets to the IRS, only income. If you disclose your income and pay tax on it then convert it to BTC today you aren’t obliged to disclose it. In theory after you sell it you’d have a capital gain to disclose.
If I pay taxes on my income earned in USD, then exchange it for Euros. If the Euros had a better exchange rate to dollars later, would I have to declare a capital gain if I exchange back for USD? What if instead of exchanging I just spent the Euros?
I am not a tax attorney, and more specifically not your tax attorney, nor a certified accountant.