Agreed. Any decision by Moody's was already priced into the market in 2017, when Fitch and S&P downgraded the country. Moody's is currently the laughingstock of the investment world and very few investment houses actually pays attention to them. Most follow the two leading agencies.
I do, however, suspect that the Rand will now start a gradual decline against the Dollar. As it becomes more clear that there is no more room to fix the country's finances, and the ANC's hands have been tied by themselves, more outflows can be expected. The outflows will most likely be accelerated by talks of nationalizing the SARB, NHI, Appropriations and EWC. This will place the Rand under more pressure.
In addition to this, government will now find it even harder to get loans to run the country. They have already struggled with this, but with a Moody's negative outlook, even less will now be available to them. I do not even think a Moody's actual downgrade is necessary any longer.