Before Peacemaker aired, I think it was DanielRPK and others of his inner circle to say the ending would've lead to a Secret Six project. You can google it. Also, Gail Simone was teasing something that could refer to the project: https://twitter.com/GailSimone/statu...32739297964035
Whoever is saying the end of Peacemaker would lead to a Checkmate series is referring to the same thing, I guess, lol.
In a recent Q&A, Gunn said he is currently writing 2 projects, the other projects he have are probably in early development stage.