I feel like the problem with Flux is the fact that there are multiple stores that the developer has to deal with. It seems easier to combine them and use a single "store" that has similar properties to Meteor, Firebase, PouchDb, etc..
You use a single, immutable data structure to store your application state, and components use functional lenses to look into the part of the state they're dependent on and listen for changes.
In doing so, you get a free application history stack and deltas (for undo/redo, offline/online sync and some powerful debugging capabilities), extremely efficient shouldComponentUpdate implementations for all components, and opportunities for many more advanced optimizations like batching updates for rendering on requestAnimationFrame.
Check out Om if you'd like to take a look at the original ClojureScript implementation, or Morearty.js if you're interested in a pure JS alternative.