The next web is not about semantics, it is about removing the gap between desktop and mobile and between installed software and SaaS. It is the post-OS era, people are using a device that is (nearly) always on and always connected, the OS and the browser are becoming commodities. It is the era in which markup is going to lead again in favor of proprietary technologies.
HTML5 is bridging the gap between the devices and the application experience, especially since all major browsers (Chrome, Firefox, Internet Explorer, Opera, Safari) are supporting HTML5 by default. Also HTML5 offers an alternative for proprietary/vendor-specific technology such as Adobe Flash, Google Gears, Microsoft Silverlight and Java FX.
Functionalities such as native video and audio, native local storage, native content editing are removing the barrier between the experience of offline installed applications and online applications. However not every user has the choice or the opportunity to upgrade to the latest version of their browser of choice, a fallback is required for most HTML5 functionality and therefore there still will be a gap between desktop and mobile and between installed software and SaaS for some users.
Markup back in the game
HTML5 is bringing markup back in the game, in favor of proprietary/vendor specific plug-in, introducing the foundation for solid cross device, cross platform, online or offline user experience and making the first efforts to bridge the gap between desktop and mobile and between installed software and SaaS.