UPDATE: None of this was announced at the recent Silent Hill event that Konami hosted on YouTube. Mira was behind it all, all along!
Things have been fairly quiet about the next Silent Hill game, but due to the way paperwork is handled, sometimes things will get out there as content is handed over to different companies in different regions.
This leak happened when a bunch of games from many different developers were submitted to the Korean Game Rating and Administration Committee. On their website (which is open and available to the public), a csv file containing game titles which have been submitted for review can be viewed. Sandwiched in the middle of the list is a game called Silent Hill: The Short Message.
Now this would usually be taken with a pinch of salt, but literally every other game on that list is a game with the correct name (including all kinds of games including Doom 3 and FIFA 23) so it can be pretty safe to assume that this will be the title of the game. It was submitted in August 2022, which is also another indication that the game is pretty much content complete, just needs tweaks from Quality Assurance and playtesting.
So yeah, there it is. Silent Hill: The Short Message