Hmm, I guess these surprises could be an announcement about upcoming dates, a song release (either new music or a leftover track), details about the upcoming album, or maybe details about their solo tracks. I have no idea
I don't think it's music related and if it is, it's not group music. Or maybe this is the "very soon" as in "months from now" in 5H language. They were just talking about getting ready to get back in the studio like 2 weeks ago so I doubt anything is set yet.