[misja111]

You have it completely backwards. Keplerian decline, i.e. the decline of the rotation speed the further away you get from the center of your solar system, galaxy or whatever, is predicted by traditional cosmology. What is detected in other galaxies, and what was thought to be detected in our own galaxy is well, is a lack of Keplerian decline. That is where both dark matter and MOND stepped in trying to explain. See e.g. https://link.springer.com/article/10.12942/lrr-2012-10

What was detected now, is that our galaxy shows Keplerian decline after all. Which, at least for our own galaxy, removes the need for introducing MOND or dark matter.

[throwawaymaths]

No. Keplerian decline doesn't mean that the entire rotation curve is keplerian. It means that it regresses to keplerian after a certain radius. You cannot explain the plateauing part within that radius without MOND or LCDM.