Season 2 starts filming next month.
https://www.avclub.com/only-murders-in-the-building-co-creator-john-hoffman-on-1847888534Quote:
AVC: What can you tell us about the second season?
JH: There's this amazing collection of stars that are already in the show. I think it's looking very happily like we're going to have many of them back again, but in fresh new ways. I don't mean new characters. I'm saying their positions have altered clearly from the end of season one.
We will be inviting back a lot of them, in ways that are hopefully surprising. Also new people that will of course be freshening up the atmosphere around the new murder that they're investigating. But also there's the investigation and then there's the telling of that story. That becomes one of the bigger themes of the show in season two: Who's telling the true story? Which feels like a big American story in some ways.