Wow! Loved the chapter! A huge tease as usual but loved seeing the New World.
I would like to think the whole act (circling, bells, prayer, and tattoo) were all a part of the message instead of it being one or the other. Especially since Rayleigh says that the crew would need to read the article rather than just seeing the picture. A timeskip seems very likely considering Nami's reaction. Like someone else mentioned, maybe it means:
Circling + 16 bells (death of old era, beginning of new): Let's meet in the new era
Silent Prayer: Stay low
Tattoo (SA2Y/SA2W): Seabody Archipelago in 2 Years or 2 Weeks (2 weeks would make more sense because of the coming break, and it's not too long where the entire One Piece world would have changed by then. Also, how long has Luffy been traveling since the beginning? Less than a year, right? So 2 years would seem ridiculous.)
This makes the perfect cover-up because everyone else would perceive each act as something different (the bells as a declaration of war or commencement of the new era and the tattoo/armband as just a tribute to Ace.)
Also, instead of wondering if Blackbeard would really kill a Supernova, the real question is from which Supernova does he have something to gain? Since, it seems like Blackbeard has figured out a way to absorb people's powers after they are killed and the chapter states that "he has made a new supernova his prey." He has actually targeted a Supernova (not necessarily meaning this particular Supernova is dead yet). It reminds me of when he targeted Luffy/Ace so that he could gain a position in the Shichibukai.