I had originally used Backbone.Model and Backbone.Collection in conjunction with React. But after reading about Flux on the React blog and watching the video explanation back in May, it only took me a week to replace all of my Backbone models and collections with Flux singleton-stores. Coupled with Andrey Popp's react-router-component[0] (now replaced by rrouter[1], I think?), I was able to remove Backbone from the project entirely.
I think that Flux is more flexible than Backbone. I really like the ability for a store to take on characteristics of both models and collections. It is also easy to combine many different external resources to compose the "one true source" of a particular type of data for many different components. I don't feel any particular need to bring back a Backbone dependency in future React projects.