Warning! Spoilers ahead for My Hero Academia chapter 334!
The sacrifice of America's top hero Star and Stripe accomplishes more than just leaving My Hero Academia fans in a puddle of tears. She bought them what they all want more than anything else: Time.
Mangaka Kohei Horikoshi made fans well aware that this current arc will be the last "chapter" in his critically acclaimed manga series. Fans have therefore been dreading the inevitable final fight because, even though it promises to be epic, the countdown to the end will begin once the first punch is thrown. The last stand against All For One was originally much closer than fans were comfortable with before Star and Stripe stumbled across him. The villain was only one mere day away from his fusion completing with his apprentice Tomura Shigaraki, allowing him to mount a full-scale assault on Japan in no time before taking on the world. But Star and Stripe's imparting "gift" to All For One left him in a vulnerable state, buying Japan's heroes about one week, according to All Might in chapter 334.
The time when All For One would be ready to unleash his true power has been in a perpetual state of fluctuation ever since he entered Shigaraki's body. Conflicting reports gave heroes false hope early on that their fusion wouldn't be complete for a much longer time period until a recent chapter dashed those hopes away - revealing that the end was nigh. Now this latest update in chapter 334 gives fans (and heroes) more wiggle room to accommodate more storylines outside the battlefield.
There are many ways in which mangaka Horikoshi can utilize this time. Before her battle against All For One, Star and Stripe used her New Order quirk that allows her to impart three rules simultaneously on separate objects (only one of which can be imposed on herself). She secretly decreed that New Order would sabotage other quirks because she knew that if she lost, All For One would try and steal it. Since the villain possesses numerous quirks, he began to explode from the inside. He saved himself by removing the quirk of a random criminal he finds using his namesake quirk and passed on New Order to him. However, he says in the unofficial translation that he's doing this for storage. It's likely that he will capture the criminal in possession of New Order to study the quirk and possibly weaponize its ability to destroy quirks according to a Star and Stripe theory.
Meanwhile, now is the perfect time for class 1-A to plan their foolish attempt at recreating the School Festival to help get the public on their side. The heroes-in-training originally created a band and performed during the annual festival to appeal to their classmates who blamed them for the heightened security at their school. Their attempt was successful, and now they are naïve enough to believe they can emulate the same effect by recreating another school festival performance for citizens who are terrified and have already formed angry mobs that were willing to risk the life of a child (i.e. Deku) to ensure their own protection.
Regardless of how mangaka Horikoshi decides to fill this time in subsequent issues, this self-imposed extension thanks to Star and Stripe gives him the ability to create more chapters of My Hero Academia without having to cram them within the course of one day.