WhatsApp for Windows Phone is one of the few apps on Windows 10 Mobile today that continues to receive frequent updates from its developer. Unfortunately, the app itself is one based on Silverlight, which is what apps built for Windows Phone 8.1 used back in 2014. This means the app isn't a Universal Windows Platform app (UWP,) and as such doesn't run across all the different Windows 10 platforms and devices available today.
That means that if Microsoft's rumored Andromeda device ever does happen, the WhatsApp app available right now won't run on it, because the version of Windows 10 that runs on Andromeda doesn't support old apps based on Silverlight. On a device like Andromeda, an app like WhatsApp is a must-have. Luckily, it appears that Microsoft may be working closely with WhatsApp in bringing its Silverlight app to UWP, along with updating its UI with a refreshed interface that features Fluent Design.
Concept art of this work recently popped up on Behance by a designer hired by Microsoft who appears to be working on the project. Unfortunately, the Behance listing was pulled after we approached the designer for comment. While the project on Behance didn't tell us much outside of what the app may look like, it does give us our first hint towards an apparent partnership between Microsoft and WhatsApp. The only context surrounding this work is a paragraph on what the project is about:
WhatsApp is a free cross-platform app owned by Facebook. You can make video calls and send text messages, voice messages, documents, and user locations. I have been supporting the team with porting WhatsApp from Silverlight to UWP. We want them to bring their app to Windows 10 desktop and integrate unique Windows 10 features like Ink and Fluent Design. The project had [a] successful result which led to WhatsApp partnering with Microsoft, and we earned high praise from the WhatsApp team.
Based on the project description, it sounds like Microsoft and WhatsApp are working closely together in updating WhatsApp for the Universal Windows Platform, which will enable it to run across different Windows 10 devices universally. Of course, while these concept images don't give us definitive proof that a UWP app of WhatsApp is in the works, it does serve as confirmation that WhatsApp and Microsoft are at least brainstorming such an idea.
Judging by the concept images, a WhatsApp UWP app would combine the functionality of both the Windows Phone app and the Windows 10 desktop app available today. On desktops, the UWP app would simply act as a "relay" application allowing users who use WhatsApp on their iOS or Android device and send and receive WhatsApp content directly on their PC via WhatsApp Web syncing.
The app would also act as a native client for Windows 10 devices that have telephony capabilities, which is why this app is crucial for something like Andromeda and is probably a big part of why Microsoft is talking with WhatsApp Inc. about building a true UWP app of WhatsApp in the first place. We asked Microsoft for comment, and they responded with the following statement: "Microsoft does not comment on rumors and speculation." So, take that as you will.
It would be super awesome if later this year, Microsoft announces a brand new, beautiful WhatsApp app for Windows 10 that works across a wide variety of Windows 10 devices, including Andromeda. Of course, since these are only concepts, even though they were designed under Microsoft it doesn't mean such an app will ever see light of day. But, at least they appear to be talking about it.