he "Beast" they are referring to is probably referring to Bete-Noir - the Futures End version of Barbara Gordon, the "Black Beast". Tension provided from the "glimpse of the future" will very likely be of the "oh man, it's going to go down bad when Babs learns that Dick and Bruce faked his death" kind of interpersonal tension.
If you think Barbara finding out Dick and Bruce faked Dick's death is gonna go down bad, just WAIT till Dick takes a good look at her and finds out Barbara's been mainlining testosterone. He seems to like his girls on the pretty side--dunno if he'll ask Barbara out to dinner with her looking like a steroid sack.