If what I've witnessed is any indication of a bigger picture, Snapchat's userbase is slowly shrinking. The appeal of expiring messages was once pretty great, but I can't honestly remember the last time I sent a Snapchat and I receive maybe a couple a week now. A few months ago it wouldn't be uncommon to receive between 6 to 12 Snapchats per day. Like all gimmicks, people grow tired and move onto the next big thing or not at all. There is only one application in the image sharing space that has remained dominant, growing quite linearly and strong and that is Instagram.
Maybe it's just my friends that have stopped caring about Snapchat and it would be interesting to see if anyone else here has noticed similar behaviour of waning interest amongst friends and colleagues and the use of Snapchat.
We all know unless Snapchat pivot the app and make it appealing again, it will only to continue to witness decline. Look to Foursquare for some great parallels, at its peak, everyone was using it at one stage and then people lost interest. The fact they had to open up yet another app got tiring and eventually people gave up. They're entering dangerous territory, it would be best for them to, tread lightly.