i heard toonami is adding a slice of life series to the block soon but is it actually true? and if so what do u think it'll be?

They’re considering comedies and horror series, I don’t recall any mention of slice of life anime from Jason.
If Toonami played a slice of life show it should probably be Yuri on Ice. It has a broad appeal and isn’t typical high school relationship dangus like most slice of life anime tend to be.
As for a comedy they might play, I honestly don’t know. There’s plenty of action comedies out there but they probably would try a screwball comedy like Pop Team Epic.