React-router4 は webpack require.ensure と連携して非同期読み込みを実現します

import React, { Component } from 'react';
export default class Bundle extends Component {
  constructor(props) {
    super(props);
    this.state = {
      mod: null
    };
  }

  componentWillMount() {
    this.load(this.props);
  }

  componentWillReceiveProps(nextProps) {
    if (nextProps.load !== this.props.load) {
      this.load(nextProps);
    }
  }

  load(props) {
    this.setState({
      mod: null
    });
    props.load(mod => {
      this.setState({
        mod: mod.default ? mod.default : mod
      });
    });
  }

  render() {
    return this.state.mod ? this.props.children(this.state.mod) : null;
  }
}

bundle-loader?lazy&name=[name]!

import Bundle from './components/bundle.js';
import ListComponent from 'bundle-loader?lazy&name=[name]!./file/List.jsx';

<Route path="/list" component={List} />

chunkFilename: '[name]-[id].[chunkhash:4].bundle.js'

const List = (props) => (
  <Bundle load={ListComponent}>
    {(List) => <List {...props}/>}
  </Bundle>
);