Huawei's flagship phones have tended to go by names along the lines of Px0 in the past. However, the OEM's latest European trademarking applications appear to indicate that this may change in the future. For a start, these alleged filings suggest that the P30's successor will not be called the P40.
https://www.notebookcheck.net/Huawei-reportedly-trademarks-atypical-new-P-series-smartphone-names.428629.0.html