Hi d20,
Yes, you are correct, we no longer develop the Isaac Sim based UE4.
We have made many improvements on the Isaac Sim based on Unity, so you can use that for now.
Our future plan for Isaac Sim is that we are working on the next generation of the Isaac Sim, until then we will be developing and supporting Isaac Sim based on Unity.
As I said Isaac Sim based on UE4 is no longer being developed or improved, and will not be supported by Isaac SDK from 2019.3 release and forward. But if you really want to use it and have questions we will answer your questions on the forum.
Hope I answered your questions,
Liila