JPMorgan Chase has raised concerns about the sustainability of the recent surge in Ethereum network activity following the Fusaka upgrade. The upgrade, completed in December 2025, increased block data capacity, reducing transaction fees and boosting transactions and active addresses. However, JPMorgan's report suggests that this activity spike may not be sustainable, citing historical patterns where previous Ethereum upgrades did not lead to lasting growth. The report highlights ongoing challenges for Ethereum, including competition from Layer 2 networks like Base and Arbitrum, and rival chains such as Solana. Additionally, the decline in speculative interest in NFTs and Meme tokens, along with the migration of major applications like Uniswap to dedicated chains, has reduced fee burning and increased ETH supply. These factors, combined with a drop in Total Value Locked (TVL) in ETH, pose significant hurdles to Ethereum's long-term growth despite the Fusaka upgrade's initial impact.