Obviously any Batman will add intrigue to the Cavill Supes sequel, since MoS underperformed from expectations. Regardless, tying it in will make it feel more like a Dark Avengers, which really is exactly what DC is hoping for. This isn't like Bruce Banner-- there wasn't an iconic Banner vision before Avengers. Whoever they pick has to be as good as or better than Bale to avoid second-week drop off due to word of mouth.

Safest bet is clearly Bale.