Users will soon be able to use a single WhatsApp account across multiple devices. The feature was first spotted in the beta version of WhatsApp, and is expected to make its way to a stable release in the near future. The chances of cross-platform support, however, look grim.
https://www.notebookcheck.net/Future-version-of-WhatsApp-could-let-you-run-the-application-on-multiple-devices.459686.0.html