We have to build what we have today. Deciding to not build a wall because we might have better technology 20-10 or even 5 years from now is dumb. We need the wall now, not 20 years from now.
Walls are not only a barrier that is difficult to get over, it is also a physical deterrent as well. Many would not even attempt if they know a 30 foot wall was in the way. Put your imaginary laser toys on top of it in 20 years for even better deterrent.
... except I did not say what you posted.