Then nothing is different.
Female mosquitoes aren't going to breed more because of this. Part of what makes mosquitoes so unpleasant is that their breeding mechanism is awkward and requires, for example, blood - our blood - to work. Finding a partner to breed with is the last of their worries.
As a result, what this boils down to is:
Status quo: virtually all females will breed with a regular mosquito, lifestyle unchanged.
Changed to: sizable numbers of females will breed with a GMO mosquito instead of a regular mosquito.
If plan works, enough females will go with the GMO, and breed shorter lifespan mosquitoes of their own, resulting in a (probably temporary, alas) reduction in the mosquito population. If the plan fails, either because the altered genes fail to do their job, or because females avoid the GMO mosquitoes somehow, NOTHING IS DIFFERENT.
What's the issue here? What can actually go wrong that's worse than the status quo? What scenario are you seeing that could happen as a result of this particular project? It's not like this is something out of a Michael Crichton novel. "We think we can reduce the mosquito population by releasing this RADIOACTIVE MOSQUITOS into the population! Their UNTESTED RANDOM GENETIC DIFFERENCES will render the entire population dead within the week! Also let's breed the mosquitos with FROGS just beforehand! Nothing could possibly go wrong!"
We know the generic differences. We know what we're releasing are otherwise regular mosquitos. This is not that terrible novel.
As someone who has good medical reasons to fear mosquito bites more than most, I sincerely hope this works. And I applaud them for trying.