According to ynguldyn on Bimmerpost.

"All re-engined F3x models will get new designations:

Model name change for the re-engined F3x: 328i (N20) -> 330i (B48), 335i (N55) -> 340i (B58).

4-cyl B48 engine will have 330i/430i designation instead of 328i/428i
6-cyl B58 engine will have 340i/440i designation instead of 335i/435i.
PHEV F30 will come as 330e, not 328e."

Link to post: