The CAD render shows that from the front, the design remains the same as the OnePlus 8T’s. There is no longer a curved display which we saw on the OnePlus 8 of this year. There is a flat-screen that has a single hole-punch cutout on the top left corner for the selfie camera. The button placement remains the same, i.e., power button & alert slider on the right side while the volume rockers on the left.
There is a slight change in the rear design when compared to that of OnePlus 8T. There is a rectangular camera module on the top left & the three circles suggest a triple camera setup. The small size of the third camera sensor suggests it might be a macro camera.
@TechDroider said that the design shown in the above image is indeed one of the few designs that OnePlus is testing for the OnePlus 9 & it is likely the one that gets finalized. As per @MaxJmb, though, it is not the final design of the OnePlus 9. So based on all these sources, it is still hard to say how the OnePlus 9 actually looks like. Stay Tuned as we will be sharing more details as we get them.