This seems to be perfectly true with Snapchat's stories. Instagram had started its own stories copying Snapchat and there is a possibility that we might see Facebook stories in the future too.
But before Facebook, WhatsApp has already started its own stories, just like Snapchat where you could post any media like images and videos you want to and it will expire in 24 hours.
Just like Snapchat, the WhatsApp stories would also be taken using an in-app camera. The stories would appear on a new status tab and can be viewed by anyone having your contact for a limited duration of 1 day. This feature would be available on Android, iOS as well as Windows phones.
Some of you might tell that Facebook already has it's own facebook stories, but thats still in testing mode and is available only in select countries.
This update comes along with WhatsApp's 8th anniversary, which was actually built to share what they're upto, which could be seen by their contacts. But according to time, this change and to keep itself one of the most used apps, WhatsApp, and all other apps will have to update themselves.
As we already said, apps do have to update to keep its users engaged, but isn't stories getting too mainstream now?
Are companies expecting users to post their stories on Snapchat, Instagram, Facebook and Messenger all the time?
Snapchat's main system is built on stories whereas Instagram is built on high quality photos, if apps want to update themselves, they should not be copying each other but do something new for the users, that is the only way an app can keep it's users engaged and happy to use it.