We've seen this before and it didn't work out so well.
Reagan signed amnesty, with the understanding that illegal immigration would be worked on later.
That didn't happen.
Dems will agree on DACA, then turn around and say they will still oppose the wall.
They have already said as much.
They agree that "later" they will work on tougher security (but no wall), vetting, etc....
If Trump doesn't get the wall before DACA goes into effect (if it does), he'll only have the previous fence act to work with.
We've seen this before.
Trump signs DACA and the Dems will attempt to block any meaningful border enforcement that they can.