I don't understand how people thought it was not-Damian. The last trailer clearly referred to him as the "offspring" which only would apply to Bruce's actual blood child, as well as the fact that he uses a sword which is very obviously Damian's gig.
Also he wears a hood which has always been associated with Damian. The only time I could think of a prominent example of a Robin who wore a hood outside of Damian was Tim in the Arkham games.
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