Apparently, I was looking at Serebii forums and one of the mods there (Wulava) shared a notable pattern with CoroCoro releases in regards to previous games when it comes to announcement of the game, and when starters/protagonists/region/mascots were revealed.
Platinum: Announced May 2008, with Origin Forme Giratina revealed a bit earlier. The following issues showcased the new characters, Sky Forme Shaymin, and updated artwork for Lucas, Dawn and the Sinnoh starters.
HG/SS: Announced May 2009, with the logos and a trailer revealed around the same time. The CoroCoro after that showed Ethan, Lyra, the revamped Johto region, and the updated artwork of the Johto starters.
B/W: Announced April 2010, with that month's CoroCoro only showing the Unova region. The next issue revealed Hilbert and Hilda, as well as the starters (who were previously shown as silhouettes on Pokemon Sunday), while outside of CoroCoro we got Reshiram and Zekrom. Following months showcased various new Pokemon and features, like Dream World and triple/rotation battles.
B2/W2: Announced February 2012 with the reveal of Black and White Kyurem. March issue didn't show any news, but April dropped a ton of information, revealing Nate and Rosa, updated Unova starters artwork, changes to the Unova region, and other new characters.
X/Y: Announced in January 2013 in a Nintendo Direct presentation, complete with a trailer showing gameplay footage, and revealing both the Kalos starters and the mascot legendaries. February showcased Sylveon, March had no news, April had Mega Mewtwo Y. Subsequent issues revealed Mega Evolution, more new Pokemon, and Calem and Serena's official artwork.
OR/AS: Announced May 2014, showing just boxart and Primal Groudon/Kyogre. June revealed Mega Diancie and the Hoenn starter Megas (Mega Blaziken was still shown despite being available in XY through event), with other issues also revealing character redesigns, new characters (including Lisia, Aarune and Zinnia) and the other new Megas.
S/M: Announced February 2016, on the day of Pokemon's 20th anniversary. So far, this month showed no news, but we do know next month will have news coming.
So based on these previous patterns, I guess S/M's news pattern is very reminiscent of B2/W2, given the CoroCoro released in March of their respective year showed no news, with the following month dropping news. Unlike B2/W2, the mascot legendaries were not shown with S/M's announcement. If B2/W2 showed its protagonist and starters (except that it was just new artwork and not new starters altogether) I'm likely expecting the next issue to reveal the starters and protagonists, but also the mascot legendaries.