Rich two-way binding based on libraries like Handlebars is the norm these days.Frameworks like Meteor are also on their way to the developer toolbox to solve concurrency & scalability issues and let the developer only be concerned about developing what they want in a high level way.
Html5 offline client-side storage features like File System API,
Indexed Database API (IndexedDB), Web SQL Database, Web Storage and
storage solutions like SQL.js, TrappistDB, PersistJS.
I know talking about Html5 WebSockets would entail another post per se. but the least one could say about it is that the future of communication in web world is persistent full duplex connection. And that can be achieved with WebSocket.