It'll be that he can't comment on an issue that is likely to come up before the court. That's almost a dead-certainty. But, I'd say the key is that he is a textualist, which is something a bit different from an originalist. Originalists tend to look for the "original meaning", and will often look outside the text of the law at issue to determine that meaning. Textualists focus much more heavily on the final result -- the text of the law itself, to determine that original meaning. To put it differently, an originalist is more likely to look at legislative history -- public statements made by supporters of the bill. A textualist (like Scalia or Gorsuch) will say that self-serving, biased statements prior to passage aren't what matter, because ultimately, what people vote on is the text of the law. And that there are often compromises/changes of heart along the way that make those prior statements inapplicable to the final product.
What that may mean in this context is that Gorsuch would focus on the actual text of the EO itself, not on all the campaign statements and other extrinsic evidence relating to a Muslim ban. And the EO doesn't say a word about Muslims.
I think he's pretty strongly in the "textualist" box, but it is very true that doesn't always dictate consistent political results.
He's sickeningly bright, though. Incredibly agile mind.
