You are correct in understanding that the Gates foundation should clarify their timelines. I am not sure why you have been downvoted for this. The economic and health impacts of malaria versus sickle cell diseases ought to be decided by the individual. If the person has no plans to immigrate and if his or her country is stuck in a perpetual resource trap with no ability to combat malaria, then the cure (eradicating sickle cell anemia) may be more harmful than beneficial.