They said after E3 that "they're still going to add more new and fun activities", and when they announced the most recent update last month, they posted a tweet saying that more free content is in development, and more information will be shared in the future. The last update (officially, anyway) has seasonal items until the end of September. September's also usually when Nintendo Directs happen, usually in the first half of the month, so there's a good chance we'll get some news then, whether that's "surprise, we put some stuff in the last update that'll keep you until November, when THIS is going to happen" or "hey, angry AC fans, here's THIS, now please never ask us for anything again (until November, next update's then)"I'm starting to get really impatient. I know Nintendo said some time ago they had something big still in store for ACNH. I think it was 2 months ago. But where is it? Sorry just had to rant a bit...
So basically, I'd say sometime in the next three weeks.