After seeing this in the May Batman group solicits thread:
I remembered seeing that sarcophagus before, in #0: Beyond A Shadow.
Now, seeing as the sarcophagus was being transported by members of The Religion Of Crime, and they got away, this means that arc four will almost certainly have Religion Of Crime elements. The sarcophagus is clearly important, and as the solicit states, "Batwoman is being played right into a confrontation with Batman…and that’s the least of her problems after the final page of #20!", so I'm guessing we'll find out what's inside on that final page.
Also, the #19 solicit states, "What is the shocking family revelation that can turn Batwoman's world upside down?". I wonder if this could mean that we'll find out that Alice is still alive. I was trying to work out if Alice would be inside the sarcophagus for some reason, but I can't work out anything logical.
Anyone got any thoughts on any of this, or any other thoughts or predictions about arc four?