If you are asking whether the proposition that "dark energy and dark matter are necessary to explain the experimental astrophysical observations within the framework of known physics" has been found false, the answer is no.
If you are asking whether it is possible to falsify the proposition, i.e. if new data could show that the proposition is false, this is always possible in physics explorations. New data trump old theories.
In general physics theories/models/propositions are falsifiable, i.e. open to refutation by new data, to be considered at all as viable.
Edit: With the link you provided for what you mean as "falsifiable" the answer is that the proposition "that dark energy and dark matter are necessary adjuncts of the theory to explain the astrophysical data " is yes, it has always been falsifiable, in the sense that new data may not fit the model and it will then be either falsified or superseded. It may take a long time to do so, as progress in astrophysics data needs money and patience, but of course it could be falsified.
Also a better model could do the job of making a model history, without falsifying it, just superseding it:
Take the example of the epicycles, when the model was a geocentric system. It has been superseded by the heliocentric one once it was realized that it could mathematically describe the system much better. Note that the epicycles were superseded, not falsified, since if you go into any planetarium program and plot a geocentric system the epicycles appear in all their glory. They just are a cumbersome and unnecessary now projection except for special cases, as in understanding the path of the planets in retrograde motion, when observing the night skies.