Uhh... i heard something from someone, i dont know wheather or not to believe it though. I truly agree that the critters will rule, and the critters may jus be the xel'naga.
Well heres the story i heard
The xel'naga created the protoss and the overmind. They created both of these very very far away so in the event the grand experiment went wrong, it would take a long time for the experiments to reach the xel'naga. They created the overmind to rule the zerg, but the overmind was out of they're control. The overmind also knew the xel'nagas only weakness, so the xel'naga It floated around space finding species like the dune runners etc. and consuming them, thus turning them into races of the swarm. It came upon the terrans and saw they're high psionic potential. It wanted to consume the terran and become invincible. Kerrigan and others then defeated the overmind. Think about it. With the overmind dead no one knows the weakness of xel naga! itsperfectly laid out. The terran at they're highest point of technology and strength, the zerg broods fighting and more vicious then ever, and the protoss rebuilding aiur and eager for revenge, duran creating the perfect hybrids, and the xel nage seemingly invincible, there you go!
by the way, the ship in the cut scene, did anyone ever bother to take a screenshot when it shows the ship and then study it even more carefully?