We now have WhatsApp on the Marketplace for Mango users as of yesterday, which turned out to be relatively bare in terms of features, but functionality is present. We've now caught word of Simon Luk from WeLoveWP.hk contacting the developers asking whether or not more functionality will be implemented in the future.

In the above image we see Jan Koum from WhatsApp stating that the team is "committed very strongly" to Windows Phone and will be adding many features as well as fixing reported bugs. So sit tight with what we have thus far, the future is looking bright for WhatsApp.

Source: WeLoveWP