I've heard a lot of people saying they want a Past time travel, and I would be one of them. So, if I were the developers, I would add a basic time machine to the base game, kind of like the space ships in there now. In fact they might just end up using the spaceship. You would have a text adventure if you used it without the pack. With the pack, you'd be able to travel with your sims in Time. They might require a different upgrade be done to it to enable the travel, like with travel to Sixam.
This way they could give you a time travel location in one pack, then later make another pack with a new location to travel to. So a Pack focusing on the Future, and another focusing on Past travel. Of course Simsville Past would be entirely fictional. Probably having certain medieval themes, but could be different. Even perhaps combining different real world historical elements into one Sims History.
If you could be the one to bury a time capsule on one of the travel tasks, it would be a cute way to explain why there are so many Time Capsules in Simsville Today. As a little joke.