This new Duolingo Blog entry appeared in my feed reader. However, currently it's not visible on blog.duolingo.com. Maybe they unpublished it because it needed another review. Anyway I thought it's interesting and I'd publish it here:
UPDATE The updated version of the article finally got published and it contains a key change with regards to who can access the feature. 
Read my comment below and read the article on Duolingo Blog here. UPDATE
(What you see below 
is the unpublished version of the article)
At Duolingo, we believe that practice does indeed make progress, and we’re always looking for creative ways to help learners review material and build on those skills as they progress along their learning journey! That’s why we’re so excited to launch the new and improved Practice Hub, a dedicated tab for reviewing previous material in a variety of engaging ways.
You can find the Practice Hub tab by clicking on the barbell image at the bottom of your home screen (on iOS only for now, but coming soon to Android!) At the top of the hub, you’ll notice two targeted review sessions that rotate daily, and below, a place to review Mistakes and Stories on-demand, whenever you want! You’ll earn different XP depending on your practice activity.
When we designed the Practice Hub, we wanted it to focus on relevant, recent material. All of the practice content is based on your recent personal activity in regular Duolingo lessons. We’ve also provided opportunities to focus just on speaking and listening, which are two skills that learners often tell us they want to improve. We’re so excited for learners to start exploring this dedicated practice space, but we know you might have a few more questions! Read on for everything you need to know about navigating your new Practice Hub:
How often does the Practice Hub refresh or add new material to review?
Every day, the two practice modules at the top of your Practice Hub will refresh and offer new, targeted practice sessions.On any given day, you might see:
Target Practice, where you’ll focus on reviewing a specific topic, like Travel
🗣 Perfect Pronunciation, featuring 10 speaking exercises
Listen-Up, featuring 10 listening exercises
⏮ Unit Rewind, highlighting a set of exercises from a recent unit
There will also be a section for your collections – a library of personalized content for practicing on-demand at any time. This includes mistakes review and re-reading Stories.
Is the Practice Hub the only way to review material on Duolingo?
Not at all! Practice is actually built into your new learning path—we use spaced repetition to ensure that you’re reviewing concepts regularly by placing specific practice levels along the path. You can also redo a previous gilded lesson or Story on the path directly. But if you want Duolingo to simply tell you what to review, Practice Hub is a great tool for doing so.Can the Practice Hub help you advance towards Monthly Quest goals?
Yes! Lessons in the Practice Hub are, well, lessons. A Listen Up module will help you complete a Daily Quest around listening practice, XP earned will help you hit your daily XP goal, and so on, depending on what Daily Quests you have on your plate!Can I review Stories in the Practice Hub?
Yes! Stories can be reviewed on the path directly, or you can access your full Stories library by going to the Collections section of the Practice Hub.
What’s next for the Practice Hub?
We’re working hard to bring Practice Hub to Android and Web learners. We’ll also be working on a few new practice modes—keep an eye out for them next year!
Target Practice, where you’ll focus on reviewing a specific topic, like Travel
Listen-Up, featuring 10 listening exercises
