You haven't been watching, have you?
Parting Genomes: UA Biologists Discover Seeds of Speciation [Happening as they observe!].
Changing One Gene Launches New Fly Species.
"...begin to become different species,"
Begin to become different species, or became a different species? Seems to me this is not what you claim. Take another look at what you are tauting.
Evolution has been held as "true" for a hundred years now, even without the "evidence" which was observed just this past June. The desire to "prove" this theory leads to biases and the strong desire to fill in the gaps of their theory. I suspect what this grad student observed isn't what they think they've observed. They've seen a change, but it's still a fly. Creation doesn't discount the possibilities of differentiations on a theme.
Whether the closely related fruit fly populations, designated Drosophila mojavensis and Drosophila arizonae, represent one species or two is still debated by biologists
In other words, the proof isn't in yet. I'm sure the researchers at UA are "positive" this is what they think it is, considering the noteriety the school would get, grant money, maybe even consideration of a Nobel Prize. But, to repeat: whether this represents one species or two is still debated.