Usually the progression of most diseases is toward easier transmission but lower mortality rates. Viruses that kill their hosts have a hard time becoming endemic.
My prediction for Ebola is that it eventually becomes like norovirus (stomach flu): a common gastrointestinal ailment that is painful and inconvenient, but seldom lethal, and spreads easily through contaminated surfaces.
Firstly, this might happen over millions of years, but this is unlikely to occur anytime in the short term. Many viruses that have been in the human population for a long time have quite high death rates in immune naive populations (think of small pox as an example).
Secondly, the mechanism of transmission of Ebola is quite closely tied to the cause of death. To be transmitted it needs to turn you into a massive viral factory and then make you very “leaky” so the virus gets spilled out into the environment. Any mutations that decrease mortality are also likely to decrease the infectiousness of Ebola
Thirdly, Ebola is starting off from a very high death rate. Even if there was a major decrease in the mortality rate (say it only kill 5% instead of 50 to 75% people), it would still be a huge problem.
"The first well-recorded European outbreak of what is now known as syphilis occurred in 1495 among French troops besieging Naples, Italy.[3] From this centre, the disease swept across Europe. As Jared Diamond describes it, "[W]hen syphilis was first definitely recorded in Europe in 1495, its pustules often covered the body from the head to the knees, caused flesh to fall from people's faces, and led to death within a few months." The disease then was much more lethal than it is today. Diamond concludes,"[B]y 1546, the disease had evolved into the disease with the symptoms so well known to us today."
It doesn't take millions of years for diseases to adapt.
Of course is doesn’t always take millions of years, but it can take millions of years and it is not something you should expect will happen quickly. Even in the case of syphilis it still took 50 years. The evolution of syphilis (to a slower disease course) is exactly what we should be most worried about happening with Ebola as it will then be more effectively spread - just because syphilis is not as quickly lethal as it once was it is not something that you want to catch and leave untreated.
My prediction for Ebola is that it eventually becomes like norovirus (stomach flu): a common gastrointestinal ailment that is painful and inconvenient, but seldom lethal, and spreads easily through contaminated surfaces.