Emin Gün Sirer, founder of Avalanche, has raised concerns about Bitcoin's long-term security due to declining mining rewards. Sirer argues that Bitcoin's economic structure may struggle to sustain miners as rewards decrease with each halving cycle, posing a greater threat than quantum computing or rival cryptocurrencies. This warning has intensified debates over Bitcoin's sustainability and miner profitability. Sirer's comments come amid broader discussions in the crypto community, including remarks from Binance CEO Zhao, who noted that while Bitcoin could theoretically be replaced by superior technology in the future, it remains a key player in the financial system today. The halving events, which reduce block rewards by 50%, have led to increased reliance on transaction fees for miner profitability. Critics warn that without substantial fee increases, mining operations may become unsustainable, potentially impacting Bitcoin's decentralization and security.