We already know there will be a line of The LEGO Batman Movie Collectible Minifigures (71017) which will have 20 minifigures in the wave but there’s some new information coming out of Eurobricks for them. Delta Customs has stated there will be 7 different Batsuits, 10 villains, and 3 neutral characters.
If you watched the SDCC trailer, there were a lot of Batsuits that were shown in less than 10 seconds so any of them could be one of the minifigures in the set and maybe even some that weren’t even shown in the trailer. As for the villains, we’ve already seen plenty of them in the sets that have been revealed so far but director Chris McKay has stated that the Rogues Gallery will be filled out in LEGO so there’s plenty of villains to choose from. As for the neutral characters, that could be just anyone’s guess.