I put the odds of the panel's opinion getting reversed en banc as roughly 4:1 in favor. There's a chance the en banc court will come to the same conclusion as the panel, but only if the draw is heavy on active judges appointed by President Trump.
It's a high-profile case; one of the many about the constitutionality of various governmental responses to the global COVID pandemic. This one's about the closure of in-person instruction at schools. Plaintiffs say that this violates their right to educate their children. California disagrees.
The panel opinion by Judge Collins holds that (1) the case isn't moot -- even though schools are no longer closed -- due to the "voluntary cessation" doctrine and the fact that schools might perhaps be closed again were COVID to flare back up; (2) the cessation of in-person instruction at public schools was fine, but (3) the order stopping in-person instruction at private schools was unconstitutional. The dissent by Judge Hurwitz agrees with (2) but disagrees with both (1) and (3); moreover, he argues that the substantive due process argument about private schools upon which the majority relies was forfeited because it was never raised by plaintiffs in their complaint or briefing in the district court.
Today, the Ninth Circuit votes to take the case en banc.
Judge Hurwitz has some pretty darn good arguments, including ones (like mootness and forfeiture) that judicial conservatives are sympathetic to in most cases -- though, here, they'd stand in the way of taking a stand on a high-profile, hotly contested political dispute. If the en banc panel draw is representative of the Ninth Circuit as a whole, I think that you'll see a majority agree with one or more of the points that Judge Hurwitz makes -- and, potentially, one of the smarter and/or more principled conservative judges might sign on to one of the procedural points that he makes. But that's by no means assured; I could easily see a draw of six Ninth Circuit judges who would go Judge Collins' way, and that's all it'd take.
Still, overall, 4-1 in favor of reversing the panel's decision. That's the line.