Came across a pic of what looks like the production model 3 series. Borrows several styling cues from the 5, anticipate the interior will be quite similar as well.
https://www.bmwblog.com/2018/09/21/new-g20-bmw-3-series-new-teasers/
https://www.bmwblog.com/2018/09/26/bmw-teases-new-g20-3-series-images-on-twitter/
https://www.bmwblog.com/2018/09/21/new-g20-bmw-3-series-new-teasers/
https://www.bmwblog.com/2018/09/26/bmw-teases-new-g20-3-series-images-on-twitter/