The iteration of blockchain technology such as sharding and cross-chain can reshape the valuation of mainstream currencies in the following ways. Sharding improves network scalability and transaction speed, increasing the usability of mainstream currencies, thus potentially increasing their value. Cross-chain technology enables the exchange of assets and data across different chains, expanding the application scenarios of mainstream currencies and enhancing their value. Overall, these technologies enhance the functionality and value of mainstream currencies, affecting their market valuation.