There is the natural capitalistic need for cheaper labor, and the wall can't address this fundamental reality. Vast amounts of dirt cheap laborers are willing to move, wanting a better life, or at least a semi-decent one.
If the wall does have any impact, it will then only greater incentivize the need/pay-off to beat it.
It becomes just another obstacle on the list of many potentially lethal obstacles already in place for the desperate to overcome.
In the long term, what can WE do to get our national check register back in black, resolve global warming, and help western third world countries become first world? Otherwise, way too soon, none of this might even matter.