What will the military be like 20-50 years from now?

I want to join the army, marines it doesn't matter to me, I am a hard worker I am 20 years old and I work construction so I'm used to heat. I am just curious as to what it will be like I enjoy being out in the heat, and I like physically demanding jobs, I don't know why. but I want the military to know what will change in the military will they still use men, because I saw on the military channel they use rc cars with mounted machine guns on top is that what will always be used in the close future Will men become obsolete.