Next step is the interplanetary competition.
The idea is that they make the next step and the final chapter is that they go into interplanetary competition.
The aliens are humanoid, like from Star Trek or something.
It could be funny and cool if executed mastermindfully.
The subplot is that there's a challenge which human race must pass to be allowed to live thousand year more.
(There's a challenge every so often, and humans passed it before~ secretly).