***** UPDATE *****
It looks like all those rumours of an EXO sub-unit are true after all!
According to a report from XSportsNews, Baekhyun, Chen, and Xiumin will indeed form EXO's first sub-unit and are scheduled to debut at the end of October.
Shortly after this report, SM Entertainment confirmed the formation of the sub-unit although it remained tight-lipped in regards to the unit name, specific debut date, and musical style.
Prior to the confirmation from SM, there was already considerable speculation about Baekhyun, Chen, and Xiumin forming a sub-unit. Following the reveal of a special video of the trio titled "Reservoir Idols" during an EXO solo concert (which you can check out below), the rumours intensified when the three recently teamed up again to sing the ending theme to "Scarlet Heart: Ryeo".
We absolutely can't wait for the debut of "ChenBaekXi", so stay tuned for future announcements!
Given that EXO have nine members, all of whom are talented in their own special ways, it would make sense to have some members go off and form their own sub-unit. While this has remained nothing more than a dream of every EXO-L, according to a new rumour that's started floating around, it appears that a new EXO sub-unit could potentially be a reality!
According to rumours on Pann, word is that Baekhyun, Chen, and Xiumin are teaming up to form a new EXO sub-unit. The rumours state that SM Entertainment suggested the idea to the trio, and all three agreed to do it. Apparently the trio are reportedly prepping a new mini-album containing five songs, and will promote it for two weeks, but nothing has been confirmed yet (obviously).
While this is nothing more than a rumour, a "ChenBaekXi" sub-unit isn't that far-fetched given that the three have previously teamed up to sing the ending theme to "Scarlet Heart: Ryeo".
We definitely need to take this with a big grain of salt and It remains to be seen how this "ChenBaekXi" rumour will turn out, but if it does turn out to be a thing, we're definitely on the "ChenBaekXi" ship!