Every species has a niche, and it's been shown that many insects are vectors for disease, and simply because the females are the only ones who drink blood is no reason to assume that a mosquitoes "purpose" isn't to help spread disease, since you do need males to help make more females.
I never said that disease-carriers would disappear or thin out because of this, simply that, as with all vaccines, the disease will lose it's potency and, if the mosquito has the purpose of disease spreading vector, having the disease be less potent also decreases the mosquitoes role in population control (something our overpopulated species needs desperately).
Finally, I find this idea to be very risky. Who's to say what side-effects this study will have, as they are modifying the malaria to serve as a vaccine of sorts.
They have just as much of a "purpose" to become food for other organisms.
How would it become less potent?
Every vaccine has the same hazards.
I wouldn't assume they "called it a day" for this research.
Obviously, as all organisms are eaten by other organisms eventually.
Less deaths from a disease equals less potency. The black plague killed millions in Europe in the 1400's, now it's curable, thus the plague isn't as potent a disease.
I doubt they've stopped either, but all it takes is a mutation in the strain they're using and a single mosquito carrying that strain escaping and biting someone to unleash a new strain of malaria on the world.
Mosquitoes, like most non-human animals, aren't easily controlled by people, and are unpredictable. I feel that this is an unnecessary risks.