For a start, if it is quite probable that scientific research will have found a cure for some lethal diseases, such as cancer and AIDS, by 2050.

will 是助动词，表示"将要"，用于构成一般将来时态。 have 是助动词，表示"已经"，用于构成将来完成时态。 will have found 是将来完成时结构，表示"到将来某个时间点已经完成某事"，这里指"到2050年时已经找到治疗方法"。