WhatsApp, the reigning king of chat apps and the subject of an absurdly large Facebook purchase, has been called "ugly" and "primitive" by sites such as...this one. On the other hand, we argued that the true genius of WhatsApp is that it works simply and cleanly. Vinfotech, an Indian design firm specializing in user interface, decided to try to imagine what WhatsApp might look like under Facebook, with a slick, new modern design.
Vinfotech isn't actually involved with Facebook or WhatsApp. WhatsApp may eventually get a redesign, if only to add Facebook's own chat protocol to WhatsApp, but it'll almost certainly be done internally, the way Facebook's newish Paper app was, rather than by an outside firm. But! That didn't stop Vinfotech from taking a crack at it, and it doesn't look half bad.
The design looks to be heavily inspired by iOS 7: all the icons (for a new post, your favorites list, chat list, settings) are thin, simple drawings. And they're in the same baseline order as the current iOS app, all arranged along the bottom of the screen. That's good; the backbone of WhatsApp's operation is that ease of finding your contacts, your current chats, and your settings. But it also adds in a lot of Facebook-specific options: swiping a contact to the left reveals an option to visit that contact's Facebook page, for example, or contact them via Facebook's chat protocol rather than WhatsApp's.
Another option it adds that WhatsApp has announced, but not yet implemented: voice chat. Voice and video chats are now included in your list of contact options when you press and hold a contact's name.
All in all it's a pretty shrewd redesign: it looks much sleeker and more modern than WhatsApp currently does, but, for the most part, it retains the simple operation that made WhatsApp a success in the first place. In the past, Facebook has shown reluctance to mess with its acquisitions very much; you don't see any Facebook logos when you use Instagram, for example. But nobody's quite sure what Facebook plans to do with WhatsApp, so this makeover is as good a guess as any. You can check out the design in more depth here.