do you mean the niche of malaria transmitter? I suppose it wouldn't be that hard for another species of mosquito to become a transmitter.
Anyway, out of curiosity i once spent some time correlating genetically modified mosquito releases with the modern Zika outbreaks (there weren't Zika outbreaks before 2007 according to WHO, only like 14 separate cases) - the Zika outbreaks started in 2007 and for the most of them it was possible to find information that there were a release of those mosquito in the area of the outbreak 1-3 years before the outbreak (in the case of Gabon 2007 outbreak it was those mosquito development and testing in previous years on an island off the cost of Gabon. Another 2007 outbreak - Yap island - also seems being a testing ground in the years leading to the outbreak).