I believe President Trump is putting the finishing touches on his plan to use his emergency powers to build the wall. He has hired a team of lawyers to fight the legal fight. If he plays this fight correctly, it will buy him enough time to put up 100s of miles of barrier before the liberal judges shut it down.
IMO there is a plan to put up the wall very quickly--within a week. The fencing has all been fabricated and loaded on trucks and staged close the border. An army (The Army Corp of Engineers) of manpower has been trained to quickly set up the fencing. The Army Corp of Engineers is in the ready. It will be SLAM, BAM THANK YOU MAM. It will be so quick, heads will explode.
Throwing up prefabs over a 100 miles in a week may be possible.
But we're talking almost 2,000 miles of border wall (or fencing) with Mexico that has to be built, less the miles that have already been built, of course.
Realistically, it will take years for the entire thing to be built.