"Everything will change when bullets travel at the speed of light via lasers."
That would make them line of sight unless you also figure out how to bend a lazer beam around the curvature of the earth without losing its power.
Excise me? I don't think we're close to getting any physical object to travel at the speed of light--let alone bullets. If we could solve this one, space travel would be a cinch. Other than that inconvenient fact, I don't think the speed of our bullets is currently a problem.
Line of sight covers a lot of distance from orbit !
mirrors, for one.
Or......
You have the laser in space and then you've got the high ground so it's always line of sight.