No, it is actually settled, only not in a court of law. The congress has the constitutional right to define citizenship and they have multiple times since the constitution was written. It will have to go to the SC so they, all being lawyers, can waddle thru the legalese in all the rule changes since 1790. Only then will the question finally be settled but for some reason I think Trump will figure out how to keep the subject on the front rumor page.
The question of Cruz being naturalized is totally settled by precedent, a body of precedent thousands of pages in length, and with 100% uniformity and agreement. This isn't some "tough" or "flexible" issue, like the extent of power enabled by the commerce clause. Naturalization is very much a cut-and-dry determination under the US constitution (no reference to Vattel, Blackstone, or anything else). Ignore precedent at your peril. In order to reverse the body of precedent, a Court, SCOTUS if you will, will have to hold that NBC includes "naturalized," opening the office to all citizens, regardless of the circumstances of their birth. SCOTUS would literally have to write NBC out of the constitution, without using the amendment process.
They could do that - SCOTUS is masters of deceit and dishonesty. But I really doubt they would want to taint the institution quite that badly. Most likely they refuse to take the issue. Chickens. Just as derelict as Congress.