That actually lead to huge AI and pathfinding problem. When out of sensor range, the computer has no idea what was there when he was in sensor range; even if it's the same turn. There should be some sort of 'What was the situation in that hex last time it was in sensor range' feature.
Yeah that's exactly what I was expecting. If only so I can keep track of who owns what system without having to have scout ships spread over the galaxy.
Hopefully we'll see something like that in the future.