Depends on how big the brisket is and how much airflow you have through your smoker.
Also, the danger zone for whole muscle meats like brisket is less of an issue (not to be ignored completely, mind you) than it is for poultry, pork and ground meats like burger and sausage.
With beef, even steaks are often cooked to only 130-135 degrees. But then they are usually cooked and eaten long before the 4 hour mark also.
Personally, I think the bigger issue is getting the brisket to the proper temperature to achieve proper fat rendering and tenderness when the chamber is only 200 degrees. You want the brisket to get up to 200-205. With a chamber temp of 200 you are going to be cooking it forever, like over 24 hours probably, in order to get it to 200, if it even gets there. And it will probably dry out during that long of a cook.
Most like to keep their cook chamber above 220. I like to keep my cook chamber about 275 personally.