(Drosophila hasn't been sunk, but D. melanogaster probably belongs to Sophophora instead. A petition to make D. melanogaster the type was denied.)
Specifically, *Drosophila* is a multiply paraphyletic genus with about 1,450 species, and *D. melanogaster* lies very far away from the type species. It's not even in the subgenus *Drosophila (Drosophila)*; it's the type species of the very distant subgenus *Drosophila (Sophophora)*. People want to split the paraphyletic *Drosophila*, but they also want to keep *D. (S.) melanogaster* as a member of *D.*, so a petition was made to make it the type species of *D.*, which would rename *D. (S.)* into *D. (D.)* and would necessitate a new name for the current *D. (D.)*. The ICZN rejected this petition, so if *D.* is split now, we get *Sophophora melanogaster*.
From a nomenclatorial point of view, I think I understand why the petition was rejected -- all that subgenus reshuffling is a bit much. From a practical point of view, however, the decision was on the stupid side of things.
(BTW, there are several insect genera with up to 2,000 species that no entomologist seems to complain about because they are, apparently, monophyletic unlike *Drosophila*.)