While Windows Phone Store is home to lots of third-party apps, you will not see a Snapchat client in there. And it is not due to a lack of effort. The company simply does not want any such offerings to be available, actively working towards eliminating and each and every one.
Rudy Huyn, a well-known Windows Phone developer, has gone as far as asking Snapchat to review the code of his 6snap client to keep the app alive in Store, but the company would not budge. Also, when Snapchat CEO Evan Spegel was told that Windows Phone users want an official app, he simply replied: "didn't think anyone used those".
However, Snapchat's could-not-care-less-about-Windows-Phone stance seems to have changed, as it just announced that a Windows Phone app is on the cards.
Answering a question about the affinity towards Windows Phone users, Snapchat's Twitter support has said that there are plans to release an app for the tiled operating system, but without mentioning when it should be expected.
@raphaeu There are plans to make it available in the future, we'll give deets when that's close. Hope this helps! :)May 16, 2015
Of course, saying that there are plans to release something in the future does not actually mean that the app will be released in a reasonable time-frame. It could be conditioned by the platform's popularity, which would not help speed things up - in 2014, its market share came in at a tiny 2.7 per cent according to IDC. Most folks who replied to Snapchat's answer seem skeptical about this too.
That is not to say that the answer is just PR talk. Snapchat has official apps for both Android and iOS, and it could simply port one of them for the upcoming Windows 10 Mobile, as Microsoft is making such things possible. It would involve allocating fewer resources compared to building a Windows app from scratch, and it would also appease users irked by its stance towards 6snap.
As usual, there will be Windows Phone users who say that they cannot care less about the availability of an official Snapchat client.
For Microsoft though it matters, as such an app would make it easier to snatch users away from the Android and iPhone camps. And this is what the software giant has been trying (and failing) to do well for years now. A win here is much-needed.