How many you can use active objects in one frame to the PC?

Maybe it could be patched in a future update to set the default max number of objects to a higher number, maybe even the 20,000 limit.

Well, if your game would need more than 20.000 active objects in one frame, it might be better to look into scripting to use external libraries that handles them somehow. Nevertheless, it's good to know modern PC's can easely handle those thousands of objects all at once!