There will be an expansion pack of Bad Batch characters for the new Lego Skywalker Saga game. That game is scheduled to be released in Spring 2021. Could this series be released around the same time or before? The Bad Batch did show up in season 7 of The Clone Wars, but I’m thinking they may want to start their series not long after The Mandalorian season 2 finishes up, just to keep the streaming going. I think the character pack DLC would make more sense after the series premiers, but I suppose the arc they’ve already been in could be enough. Just wishful thinking.
It would most likely start streaming in a similar timeline to Clone Wars’ final season, winter 2021, give or take a couple weeks, as it’s the almost entirely the same team (writers, animators, editors, etc… give or take a couple new hires).
Mandalorian shifted a week or so between seasons, so maybe Bad Batch will be slightly earlier in 2021 than Clone Wars was in 2020… or maybe it’ll be slightly later due to COVID-19. Disney may not have even decided yet.