Bitcoin users who do not migrate their coins from legacy wallets to quantum-resistant wallets by the Quantum-Resistant Address Migration Protocol deadline will lose access to those funds, as transactions from legacy addresses will be rejected by the network

Quotes that support claims

Cruz’s QRAMP proposal outlines how the hard fork would work. Once activated, it would trigger a countdown. Users must “sweep” their bitcoins from vulnerable legacy addresses to new quantum-resistant wallets. If they fail to do so before the deadline, Bitcoin Core — the dominant full-node software — will automatically reject any attempt to spend those funds.

At the heart of Cruz’s proposal is a controversial idea: force users to move their funds from older, quantum-vulnerable Bitcoin addresses to new, quantum-resistant wallets. If users don’t comply by a set deadline, their funds could be effectively destroyed.