Messaging apps are definitely posing a challenge to mobile OSes, particularly in countries where open web access is limited and consequentially browsers have lower utility. However, this time around the competing platforms are working on incompatible standards unlike the browsers in the 90s which largely adhered to some form of specs. Plus the user bases have a lot more zeroes to them and are heavily entrenched.
It also makes it pretty clear why Facebook has been doubling down on Messenger and their acquisition of Whatsapp. Possibly a matter of time before the two start talking to each other. The really interesting things will happen if they ever start talking to other messaging platforms.