What Does The Ending Of Fantastic Beasts Really Mean?

6. The Obscurus

Grindelwald's discovery that there are other Obscuruses in the world, and that they can be removed from their host bodies - as revealed by Scamander somewhat by accident - and potentially "used" to pull down the veil between the No-Maj world and the Magical community to start a war is a small but very key detail.

So too is the fact that Scamander still has another Obscurus in his possession, making him an important target for Grindelwald if he decides to continue his same plot with a new host for the Obscurus. Given his fascination with that revelation, it would be odd for it to be dropped entirely.

This could be how he's drawn back in on his new enemy's escape (because it's unlikely he would be interested in any of the other magical creatures). Or maybe it's another character link entirely...?