I don't think it would be that out of character for him to become Batman if Bruce dies or disappears. He is mature enough to take over the identity if he feels it is needed for Gotham. It depends how much of a timeskip they will want to do in the future. Damian is still just a baby, so they would need to jump forward 10 years if they want to do a version of Dick and Damian as Batman and Robin. Which would age up their whole cast into their 20s now. That would be a bit tough to pull off I think. So there are some things like that making it difficult.
I always thought it would be more likely to happen if there was a glimpse into the future like with the world controlled by Darkseid and Dick would be Batman there leading what is left of some resistance. Like instead of Wally being dead he got sent to that future and runs into Dick as Batman. I can envision something like that happening more than it happening in the normal timeline, but they want to keep Wally as being dead so that whole scenario seems unlikely too.