I'm also curious as to how you put 2.50 billion on one ship? Can you imagine just how big that ship would be? I know, I know: it's just a game (and I've been down this road before), but so was Outpost and you were hard pressed to put more that 200 (not b nor m or even k - just 200) on your one ship that was going to save the human race.
Just for the fun of doing this. The largest ship according to this page: http://en.wikipedia.org/wiki/List_of_world's_longest_ships is 488m long. Now with the technology of hyperdrive they might solved the stasis problem and they can just boxed as merchandise (5th element, just cruder). If we said that each box is 2.5x1x0.5m (1.25m^3) and a cargo space would be 500x50x20m (500,000m^3) without considering engines and other things you could say that you can store 400,000 boxes. Now, a simple 500x500x500m can store 10,000,000 boxes. So, 200 is not a problem unless you wish to treat them as non storage things, sorry, people (Yor is easier, lol).
Now, there are other options that would satisfy the share quantity of 2.5B people: fast growing embryos, meat processors in which the store the knowledge/memory of the travelers and reconstitute their bodies as a meatballs, the colony ship is really a teleporter with a limited quantity of energy to do a mass recall (one module = 500m people teleported), they are de-materialized, stored as quantum energy and materialized in the new planet. Etc, etc, etc...
