How Every Robin Can Appear In The Batman 2
7. Damian Wayne
Most versions of Robin could in some form be fairly easy to adapt to any upcoming film and, in the case of multiple Robins, potentially fit into a narrative with only limited lip service given to backstory. The same cant be said of Damian Wayne. His background has major implications for both the characters and the plot of any Batman film he might be a part of.
Bruce finding out that he's a father is a big deal. Fatherhood would necessarily become the driving force for his character development. Then bring in the League of Assassins stuff and Damian becomes the centre of the plot.
It all sounds great, but premature for the second film.
However, there is a way to include Damian in the next movie without making it about him. In "Robin: Son of Batman", it is revealed that the young Wayne spent a year doing missions for the League of Assassins in an initiation called the 'year of blood'. Adapting this plot and introducing him under an alias while on mission could work.
If, for instance, they were to run with the "We Are Robin" idea, Damian might be brought in as just another of the Robins. His true identity could be a fun reveal and would serve as perfect sequel bait. And if his alias happens to be a name fans will recognize like, say, Terry McGinnis, who was technically Bruce's biological son, it's just gravy.