According to TechCrunch, Instagram Stories is stealing Snapchat’s users 
So yes. It looks like some users has gone to Instagram Stories. You can't blame users though. It's hard to find celebrities on Snapchat. While on Instagram, almost all celebrities are already on the platform and you can easily find them. And all of them are marked "verified". Unlike on Snapchat, there are some celebrities who aren't verified. So you don't know who's real and who's not.