As you mentioned, U.S. District Judge Derrick Watson issued a temporary restraining order which blocked the travel ban from being enforced. The judge mentioned Trump's comments on the campaign trail and based the ruling on the administration's potential intent to ban Muslims from entering the US.
Quoting from this article by CNN - the "ruling is almost entirely based on the
'intent of the Trump administration'".
The judge said it was illogical that the ban was not motivated by religious discrimination.
"The illogic of the Government's contentions is palpable," Watson wrote. "The notion that one can demonstrate animus toward any group of people only by targeting all of them at once is fundamentally flawed."
"Equally flawed is the notion that the Executive Order cannot be found to have targeted Islam because it applies to all individuals in the six referenced countries."
(emphasis mine)
However, on the same day, the judges on the Ninth Circuit Court, which upheld the first TRO in February, issued an opinion1 that the revised Executive Order is constitutional.
whatever we as individuals may feel about the President or executive order, the President's decision was well within the powers of the presidency.
1The opinion issued by the judges on the Ninth Circuit Court in this case is not a decision, but a dissent from a denial of an en banc rehearing. So, the opinion isn't legally binding nor is it considered a ruling.
So,
Whether it's constitutional really depends on the perspective:
Basically, if you read the text of the Executive Order, there's no mention that it discriminates based on religion and this makes the EO entirely constitutional. However, the judge argued that Trump's comments on the campaign trail may suggest the actual intent, thus making it unconstitutional.
This paragraph from an article by Politico summaries it:
In the end, the administration’s deepest constitutional problem in this affair is entirely straightforward. The order is in fact animated by prejudice, and pretty much everyone knows it. To be sure, there’s no guarantee of how the judiciary will ultimately rule on this order; as with so much else just now, we are in uncharted waters. But when a powerful person in the public eye does something that he promised to do, the way that his organization executes the task will leave telltale signs about its motives. Our actions do usually have some connection to our actual intentions, after all. And if those intentions were previously announced, it’s harder to convince people that they aren’t seeing what it looks like they’re seeing.
(emphasis mine)
-
Whether how the Supreme Court will rule on this:
It still waits to be seen. As the Trump administration has mentioned that they are going to appeal the ruling, it will be heard in the Ninth Circuit Court. So, there's a chance that it will the TRO will be cancelled since the judges have issued their opinion that it's constitutional.
