Graph below, published on Statista shows a fabulous growth in WeChat subscribers which is phenomenal and the credit must go to the company Tencent Inc., China's largest Internet Service Company, that not only knows the nerve of youth but is able to foresee requirements beyond today.
Top 10 most popular instant messaging apps in the world by Xinhua and China Daily shows WeChat at number 3 and same is on Eastday in a report published in March 2014.
In a survey/article published in Readwrite.com on "10 Most Popular Mobile Messaging Apps in the World" - WeChat is again on number three.