WeChat's "App Revolution" is by no means a technical revolution, as several other commenters have pointed out. There's nothing new with embedding a web browser, nor with SSO, or integrated payments.

The revolution is the fact that this is an app with an install base approaching one billion users (846M monthly active users as of Q3'16). Anything they do is potentially revolutionary by virtue of sheer scale. They are a platform as influential and powerful as Facebook is in the West. If they decide they want to compete with the platform's application store, they will provide strong competition.

WeChat has already beaten out most other payment methods in China for day-to-day commerce - credit cards, cash, cheque, etc. It has beaten out most social networks there (after the introduction of the "Moments" feature), and all other instant messaging services including SMS. Taking over other application functions is simply a natural progression for the rather unstoppable juggernaut at this point - and third party app developers will be happy to oblige.