The site discovered details about the unreleased version in the Update History section of the app's description.
Upcoming Twitter 4.3 Features:
● Discover more interactive experiences inside any Tweet: when you view tweet details contianling links to partner websites, you can now see content previews, view images, play videos and more
● Special experience around selected events: we'll curate accounts and surface the best Tweets and photos from those involved
● Improvements to autocomplete suggestions when you search for people in Connect
● Push Notifications for Tweets: you can know immediately when selected people you follow have tweeted
● Ambient notifications: enables you to see brief non-interruptive notifications in the status bar while you are using the app
● Discover: now indicates when new stories are available for the user to load
● Trends: support for personalized trends
● Tappable avatars that take you directly to user profiles
● Performance improvements
● Support for password entry in app when experiencing authentications issues
● Hungarian language support
● Updated with new Twitter bird
● Many other tweaks, polish, and bug and crasher fixes
It's unclear when this new version of the Twitter app will become available. The updated history was posted on July 6th.