Thos is just a formality. If the IRS have been encouraging taxpayers to file NFT holdings accprding to its purpose then it's only a matter of time before a specific law is introduced. 
As far as I know, it would be impossible for government to put taxes on decentralized market.
You really believe NFTs are decentralized? This is like saying Tornado Cash is decentralized until the Government made its move. Keep in mind that anything that generates profit is generally taxable in all places unless there's a specific law that says it's not.