(I'm not an expert,i have limited knowledge on the subject) Much more likely is resistance to UV without changes in transmission route, so it survives longer in droplets. However there is a (tiny) chance of "recombination" with another airborne RNA virus that is "compatible", where two viruses share genetic material while infecting the same cell and the resulting hybrid is viable "airborne Ebola", however it would be sharing traits of both viruses. Some links: https://www.sciencedirect.com/topics/medicine-and-dentistry/... http://www.recombinomics.com/News/11150702/Ebola_Recombinati... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3787895/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3324781/

Ebola would have to change a good bit to become airborne. If that were to happen, it would be a very different disease and there is no reason to assume it continue to be nearly as deadly.

Why would becoming airborne make it less deadly?

Genetic/phenotypic trade offs.

It does, the more a virus replicates the more opportunities there are for a mutation to occur. The probability of specifically developing an airborne vector is pretty low though - there are significant differences between the physical properties required for fluid vs airborne transmission. A lot of specific mutations would have to accumulate, and there is no guarantee an airborne variety would see the same level of success and persistence as the original.

The good news here is that virus genomes are usually so small and parsimonious that they find it hard to cross significant fitness valleys between different local maxima. But they also have monstrous cohort sizes, so it's not impossible for them to get "lucky." (Lucky for the virus in a Darwinian sense, unlucky for its host.)