The May issue of Bessatsu Shonen Magazine, which contains the final chapter of The Attack of the Giants, sold out in Japan at supersonic speedswhere Kodansha has already ordered the first reprint "with great urgency". It had never happened before that the magazine sold out so quickly.
According to the editor of the series "Attack of the Giants # 139, the record is sold out in one store after another" and as reported by Comic Natalie The magazine won't be available again in Japan until April 30th. So at this point it is plausible that there is a gap of at least a week that the month will not be available, a situation that has only occurred with Demon Slayer in recent years: Kimetsu no Yaiba # 205 on Weekly Shonen Jump.
For Hajime Isayama's manga, this is, of course, an extraordinary result, which is no surprise given the popularity of his great work. The final volume of The Attack of the Giants will be released between May and June 2021and we shall probably see a similar situation during this period as well.
We are waiting to find out if Isayama will decide to start a new series or work on the world of The Attack of the Giants again, maybe with additional chapters or spin-offs. We remind you that there is still an anime course waiting for us in winter 2022, re-created by the MAPPA people.