I do not think Instagram has reached its peak as a social media. Although Instagram has great features, it still lacks in some aspect, and if it does not fill that void, another social media platform will take its place and give the public what they want.
This will, in turn, cause a decrease in the use of the app for a company to reach its peak, it means the company has filled all the void and are way ahead of their competitors, this includes creating new features that will make the usage of the app convenient, and worthwhile. However, Instagram is lacking in a lot of features that its competitors are having. For example, the Chinese website allows you to exchange money and still chat with other people and share pictures.