There is a new paper on dolphin molecular phylogeny: https://www.sciencedirect.com/science/article/pii/S1055790320300282
The paper shows that:
1. Burrunan dolphin is not a valid species (but a good subspecies).
2. Genera Stenella, Delphinus and Lagenodelphis should be lumped (Delphinus has priority). This actually has been clear for some time, but here’s another confirmation.
3. The authors say Tursiops should be kept as separate genus because it’s monophyletic, but I think it should be also subsumed into Delphinus, considering the long history of hybridization.