Justin Sun Turns Bearish on Bitcoin (BTC), Citing a Two-Year Upgrade Barrier

Update 23:56 UTC: Additional details from the interview, which Sun gave to William Joy on October 16, 2026, sharpen the technical framing of his warning.

Justin Sun's Two-Year Upgrade Warning

Justin Sun has turned openly bearish on Bitcoin (BTC), arguing that progress in artificial intelligence and quantum computing makes the network's risk picture worse than most holders admit. In an interview published last week, Sun said neither the wider industry nor investors exposed through ETFs have priced in the two threats, even as the Bitcoin price hovers around $81,900. His sharpest point concerns timing: mathematical advances driven by AI could, in his view, allow ordinary computers to break today's cryptography before true quantum machines arrive. The heart of his case is the network's own speed of change. Sun said most people in the crypto industry do not grasp how slow the consensus mechanism behind the proof of work design really is, and he called a full network-wide upgrade within two years nearly impossible to complete. He aimed at Wall Street as well, saying managers at firms such as BlackRock devote far too little research time to the problem while their clients hold the asset through the same ETF wrappers he criticizes. His own position deserves scrutiny. Sun operates Tron, a competing chain that is implementing the post-quantum standards issued by the US National Institute of Standards and Technology, with a mainnet upgrade expected as soon as next year. That rollout gives him a first-mover story in post-quantum readiness, and it is the lens through which his bearishness on the largest chain should be read. On the two-year figure he was categorical: the network has never moved that fast, and in his telling it will not start now. The warning reaches a Bitcoin (BTC) market that had largely filed quantum risk under theory.

The technical backdrop behind Sun's warning has moved since he spoke. Google Quantum AI estimated in March 2026 that fewer than 500,000 physical qubits could break Bitcoin's cryptography, roughly a 20-fold cut from earlier figures, and on October 15 researchers showed magic state cultivation on the Willow chip, cutting errors about 40-fold with 99.99% fidelity in a paper published in Science. Willow carries only 105 qubits, but the result targets a major bottleneck in shrinking future attack machines. Sun also put a number on the exposure he fears: once decryption arrives, dormant coins with visible keys could be breached, and in the worst case selling pressure could exceed 2 million BTC, a mess a hard fork could not fix given how hard consensus is to reach. Coinbase, which custodies a large share of supply, published technical considerations on October 13 urging preparation through flexible output types and staged hybrid protection.

Additional details from the interview, which Sun gave to William Joy on October 16, 2026, sharpen the technical framing of his warning. Sun pointed to Shor's algorithm as the tool a sufficiently powerful and error-tolerant quantum machine could use to derive private keys from public keys, a threat to the ECDSA and Schnorr signatures Bitcoin (BTC) relies on, while hash functions such as SHA-256 face a different risk profile under the same attack class. NIST, which issued its first three post-quantum standards in 2024, itself treats public-key cryptography as a future quantum target, though no practical device capable of breaking Bitcoin's signatures exists today and no verified classical break via AI has been demonstrated. Sun's position, on this reading, is a hedged call on future mathematics rather than a claim of any current breach.

@WuBlockchain · X post

An interview published last week.

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Arthur Hayes Counters With Address Hygiene

Arthur Hayes pushed back in his own interview, and his message was that nobody should sell Bitcoin over quantum computing. The fix he describes already exists at the holder level: keep wallet addresses clean, move coins out of exposed addresses and sign transactions with current schemes. “Use the latest signatures. Don't use wallets Satoshi used,” he said, adding that whether the threat proves real matters less than people assume: as long as Bitcoin does not fall to zero, the question becomes irrelevant. In effect, Hayes is telling the market to HODL while the protocol debate plays out. He has run this line before. On October 8 he described AI-related worries as the latest wall of worry ahead of a new bull run, and a week later he dismissed the AI spending boom as wasted money whose collapse would eventually force money printing, which in his view lifts Bitcoin. It is a thesis with institutional echoes: JPMorgan has its own 10% annual return forecast for the asset. The data sits between the two men. Glassnode estimates that more than $500 billion in Bitcoin is held in addresses whose public keys are already exposed, precisely the exposure Hayes says routine hygiene removes. Satoshi-era coins, the largest single crypto whale hoard, cannot follow that advice unless their dormant owner returns, a gap no signing scheme fixes. Google's quantum announcements and a broken computing record have kept the subject alive, and nine blockchain organizations have now formed a coalition to coordinate a response. The market context has stayed orderly: Bitcoin held above $80,000 in the weeks after the October drop, as our earlier report on the $80,000 hold noted, and the tape now works near the $81,356 support level we flagged on weak ETF demand.

@pete_rizzo_ · X post

His own interview.

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The disagreement is narrower than the headlines suggest: both men accept the threat exists and differ on how fast the network and its holders can realistically respond. Sun's two-year limit is a claim about collective coordination, and it doubles as a showcase for Tron's own NIST-aligned upgrade due next year. Hayes's answer is available to essentially every holder today, and Glassnode's $500 billion figure measures the population that would need to act, though the Satoshi-era stash sits outside that fix. Which side ages better will be settled by upgrade schedules rather than by interviews.