There is one workaround that is entirely in developer hands, but starts from scratch:
https://community.leapmotion.com/t/protocole-usb-for-robotics-apps/731/3
This might get you multiple leaps, but none of the image processing and heuristic hand reconstruction. Depending on your intended application and use case, this might actually be an advantage.
It also requires reverse engineering the USB initialization protocol for the controller. Leap could release information and/or sample code regarding the USB communication to facilitate, but there are not enough developers interested in using more than one leap. Worst case, the current firmware is not able to handle two devices on the same bus.
There has been no progress/change on this issue for over a year. It is not a priority for web/apps/store development.