I recall reading something saying it's not going to happen until tomorrow and it will be a larger scale EO than originally thought.
Edit -
I found it, and thanks to Meclazine for posting it -
From CNN
"Officials said Trump would wait until later in the week to take action on visas and refugees, potentially as early as Thursday.
An order being prepared for Trump's signature includes the drastic measure of suspending the entire refugee program for four months in an attempt to gauge which country's migrants pose the least risk for US national security. A program for admitting Syrian refugees, who are fleeing civil war and a humanitarian crisis, would be ended indefinitely."