Constitutionality here is a matter of interpretation, one that the courts ultimately decide.  If constitutionality were the issue, then a court decision would have decided the matter, so the rational course of action would have been to take the matter to court.  As it stands, the question of constitutionality hasn't been addressed.  So, from a practical point of view, your claim of constitutionality is a red herring.

The Trump administration's action rescinding DACA seems to have been calculated to make people play the "what if" game.  Indeed, your prediction that Congress will pass some kind of amnesty is predicated on Congress contemplating "what if" in an election year. 

At any rate, I hope you are right and that Congress resolves this issue in favor of the DACA kids, whose demonstrated desire to achieve the American dream can help keep America great.