I know that DC will never permanently retire Bruce Wayne as Batman.
And I know that in any given continuity where he does retire, even temporarily, he'll almost certainly be replaced by one of the better-known, male Robins/ex-Robins (especially Dick).
But really?
It should be Cass.
Cassandra Cain is not only probably the best fighter of the group, she is the one who most embodies Bruce's core values, who takes his rule against killing, and his belief in trying to save everyone, most seriously. She admires Batman, and what he stands for, deeply.
Also, and I know I'm not the first person to say this, but others have grown into their own hero identities separate from Batman, in ways where becoming the next Batman would feel like a step back for them. Especially Jason, but also Dick, Babs, etc.
Whereas to Cass, it feels more like the culmination of her arc, at least to me.
Admittedly, she'd probably be one of the worst at filling the role of Bruce Wayne, and I don't know how well she's match Bruce as a detective (not saying she couldn't do it, just that its not the first thing you associate with Cassandra Cain). Tim would probably be the best fit in those roles, from my limited knowledge.
But I honestly think that having someone who truly understands and embraces the values of Batman is more important in a successor than exactly matching Bruce's skillset.
And that's Cassandra Cain.
(Okay, the best possible successor skill-wise would probably be for Cass and Tim to split the Batman duties, with Stephanie along to lighten them both up. But if we're just picking one, Cass).
Just give us one continuity where Cass succeeds Bruce.
