The future of the NaCl WebPlugin is uncertain, as it has been deprecated by Google in favor of WebAssembly (WASM). However, the technology and concepts developed through the NaCl project continue to influence the development of web technologies, and its legacy can be seen in modern web technologies such as WebAssembly and PWA's.
Early versions of ChromeOS relied heavily on NaCl to run complex local applications (like the Chrome Remote Desktop app) before Android and Linux app support were natively integrated into the OS. Why Did Google Deprecate NaClWebPlugin?
Before Native Client (NaCl), running complex desktop-grade software in a browser required insecure, platform-specific plugins like Adobe Flash, Microsoft Silverlight, or Java Applets. NaClWebPlugin changed this paradigm by introducing a secure execution environment built directly into the browser architecture. How Native Client Technology Worked