The Talmud, Tractate Sanhedrin [97a]: “Rav Kattina said: ’The world will exist for 6000 years and one (thousand) of destruction’. What is the hashkafic reason to only have a finite world? Wouldn’t an infinitely good G-d want more souls to bestow good upon?
It’s true that altruism (“bestowing good”) is a very basic and important Godly trait, but the complex world and accordingly, the multi-faceted and intricate midrashim, deal with many other issues, as well. The concept of Shabbat (every 7 days), Shmitta (every 7 years), Yovel (every 7 Shmittas) and a Sabbatical rest for the world (even an entire 1,000 years!) are basic concepts as well. Reward and punishment are also central themes of creation and the midrash, and they may also be part of the message here. In short, we don’t know which midrashim are meant to be taken literally, but in any event the main point here, as usual, is the moral or philosophic message that the Shabbat is inherently built into creation, and not necessarily an historical prediction or literal tradition.