Hundreds of thousands of religious extremists are set to march on Jerusalem. Whether or not "hundreds of thousands" will descend on the Israeli capital is to be seen. My guess is that the turnout will be less than expected, but still there will be a sea of black hats.
In preparation for this event, Israel has ordered streets closed, trains to stop running, and buses to stay at the bus station.
Whether or not the risk of the mass demonstration occurs - in any volume - the risk already is impacting the capital.
The impact is that people won't be able to
* Go to work
* Go to school
* Go shopping for essentials (bread, milk, etc.)
* Get to a hospital or clinic if necessary
Essentially they are trapped in their neighborhoods, if not their homes.