Donald Trump signed an Executive Order which does not end the Zero Tolerance policy, does not change the revocation of domestic abuse or fears of gangs as grounds for asylum, does not change in any way much of anything except they will apparently not separate families but instead detain them together.
There is also no indication that this order will pertain to the children already taken from their fathers and mothers.
Josh Marshall's analysis seems right:
The problem is that that violates a 1997 consent decree saying that you can’t detain/imprison children for more than 20 days (technically what’s currently happening isn’t detention). It straight up violates that order. So what will almost inevitably happen is that a court will step in, say you can’t do that and then Trump will announce that the judge is forcing him to keep separating families.
And as Chris Hayes notes in the video above, there's no way to know how this will be implemented. Assuming that it will apply to the children already separated, they are unsure how they will even reunite them, given the complete lack of tracking and matching of parents to children.
Baslcally, Trump bought himself a tiny sliver of breathing space and little more. He's losing this battle, and if he thinks he'll win the midterms with it, he may be in for a terrible surprise.