Back in June the producers of the show decided that “moving forward, The Simpsons will no longer have white actors voice non-white characters.” At the time this was just a decalrative statement with no further explanation.
We still don’t have details but we do have news. Alex Desert, who starred in the Flash and Better Things, will voice Carl in the premiere. The Hollywood Reporter reached out to the show and they declined to comment. But they did release another statement which read, “We are very pleased to welcome Alex Désert, playing Carl in the Simpsons season premiere.”

At the moment it’s unclear if this is a permanent change to the roster or if its just a guest appearance. The wording of their statement reads both ways but, to me, skews in the latter direction. At the very least this shows that The Simpsons will try to make good on their promise.
Hank Azaria formerly voiced Carl and while Azaria has stepped down from portraying South Asian character Apu, he continues to provide the voices of other Black, Indigenous, and People of Color (BIPOC) characters like police officer Lou, and Hispanic character Bumblebee Man. As to what will happen to these characters remains to be seen. There are still plenty of other BIPOC characters on the show and how the producers handle this will be an interesting thread to follow this season.
Season 32 premieres Sunday September 27, 2020.