I'd be surprised if the Supreme Court arrives at a clear majority opinion that Congress lacks the power to grant the President "extraordinary powers" during a time of a declared "national emergency."

Again, that's not the issue at stake.

Congress can grant the President extraordinary powers during a time of declared national emergency. And they did. They listed them, right in the IEEPA. A whole bunch of things he can do:

investigate, block during the pendency of an investigation, regulate, direct and compel, nullify, void, prevent or prohibit, any acquisition, holding, withholding, use, transfer, withdrawal, transportation, importation or exportation of, or dealing in, or exercising any right, power, or privilege with respect to, or transactions involving, any property in which any foreign country or a national thereof has any interest by any person, or with respect to any property, subject to the jurisdiction of the United States;

...but they never said he could impose tariffs, taxes, imposts, duties, excises or anything like that. Which is the main issue before the Court. None of those words is a synonym for "tax" or "tariff." The power to impose taxes and tariffs is a different power than the power to regulate.

The Court is grappling with whether Congress did grant the President the power to impose tariffs (only Gorsuch seems interested in the question of whether they had the power to grant it). ACB and Roberts are wrestling with whether it is at all sensible to believe that Congress would convey the power to impose tariffs without using the word tariff, by "hiding" that power in the more general word "regulate" rather than just say "tariff" or "tax."