Not quite. If the goal is to last as long as possible, it means that something must happen in one of the rounds that will bring you victory! But the Orcs will lose anyway :)
Not entirely correct. The Orcs lost the rebellion, but not the battle:
The survivors scatter in all directions, including to the southern deserts, the northeastern steppes, and the eastern Border Islands. A terrible storm sinks the Empire's fleet, which was following the islands to capture the fugitives. The Emperor takes this as a sign from the Dragon Gods, and the persecution of the Orcs ceases.
So, if there were timed rounds, it would be possible to defend against the fleet that was gradually approaching the islands until the storm arrived.
But again, these are just assumptions; what will actually happen will only be seen after the game is released :)