Recent renders have indicated that Huawei intends to stick with a round housing for the rear cameras in its upcoming additions to the Mate series of high-end phablets. A newer leak appears to corroborate this detail. It shows that both the 40 and 40 Pro will have at least 3 sensors apiece within a bordered circle of what looks like glass.
https://www.notebookcheck.net/A-new-leak-may-confirm-Huawei-will-keep-on-circling-the-square-with-the-Mate-40-series-rear-cameras.488657.0.html