Oh, there's no question it won't get built. For 3 reasons:
1. It's impossible. The reason there is not a contiguous wall now, is because the terrain does not allow a contiguous wall to be built. Something like 900 miles of that border is simply the Rio Grande River. Rivers move. Walls don't. So if you build the wall far inland inside of America (thereby walling off any American access to the Rio Grande itself, bythefuckingway), to try and put the wall far enough away from the river that the river doesn't eventually wash up against the wall and undermine it and make it fall over.
2. It will make the US smaller. You can't build the wall in Mexico, because you don't own Mexico. But there are thousands of American's property who bump up against the border. Now you need to pay every one of those people to take their land (and build a 50-foot wall on the south side, which will block the sun and cause your lawn to die), or even better, seize their land using Eminent Domain! Now, I don't know how well you know Texans, but they ain't gonna take kindly to the U.S. Government coming in a seizing their land and building a big fucking wall (that they don't want) on it. That ain't going to go well for anybody.
3. It's a bogeyman. The "problem" the wall "fixes" is apparently "illegal immigration". Thing is, for the last fifty years, illegal immigration has been going down, and in the last 8 years - due to Obama's truly nasty treatment of immigrants - there is a net outflow of illegal immigrants from America. We LOSE more illegals every year - by their own choice, not through deportations - than we gain.
80% of illegal immigrants arrive in America by fucking airplane, anyway! I don't care how tall or "yuge" your wall is... it ain't stopping airplanes.
A wall can't do anything about the thousands of tunnels that bring people and drugs UNDER the border into America. And this happens in places where we HAVE a well-defended wall, and Border Guards! Build a 50-foot wall in the boonies, and you will find 51-foot ladders. (There's a great Border Guard podcast that talks about when the current wall was raised from 13 to 20 feet. They collected so many 21-foot ladders they ran out of ROOM at the border guard's dispatching offices.)
Not to mention that every single agricultural business from Arizona to Ohio is going to have a fucking conniption when they can't get enough seasonal workers to pick their harvest before shit goes bad. Because I guarantee you that perky little cheerleader Madison and high school track star Curt, aren't going to pick cabbages for $20/day.
No, in short, the wall will never be built. Because at some point, some business has to place a bid for the project (or their part of it). Their engineers will go out there, look at the terrain, design something that will kinda hold up under most conditions (see: New Orleans and Hurricane Katrina to see how well THAT works out) and the numbers don't balance.
Illegal immigration MAKES the US an enormous amount of money. Cutting off that flow of money will affect big business, and those people will go knocking on the Oval Office door, and have some very nasty words to say to Tinyhands McDickpunch.
The economy is the American God. If you fuck with the economy, you go down. Period.