The Batman: 9 Things That Are Impossible If Ben Affleck Returns
2. Robin Appearing At All
The time for Robins in the DCEU has passed. We know that Jason Todd is dead, and that his death had a profound impact on Batman (to the point where he isolated himself and refused stead-fastly to work with anyone else), and we also know that Nightwing is coming, as that spin-off movie has been announced already.
Both of those facts make it supremely unlikely - at best - that we'll get to see Batman team up with a young sidekick (no matter how much Affleck would work as a torch-passing character). No amount of working with the Justice League will convince him that putting someone else in the firing line - as he did Todd - is a smart idea. Certainly not someone who isn't super-powered like The Flash, anyway.
This Batman is a lone wolf, which is exactly as it needs to be for the Nightwing story logic, and it's illogical to imagine that he'd take on an apprentice at this stage.