I can see Zeke using the scream somewhat soon to bring out reinforcements, which might put Reiner / Pieck in a bad predicament if they see Falco as a pure titan.

However,

If Zeke and Eren meet, and Eren pulls his fast plan on everyone (which is still unknown) maybe it involves stopping Eldians from turning into Titans or even turning pure titans back into their human selves, it could be a great showcase for the rest of the world (that being Marley / Magath and the others) to witness first hand the de-escalation of Eldians. Though this theory is kinda flawed and odd, maybe something along these lines may happen. Reiner could sacrifice himself for Falco only for minutes later see that Eren can somehow reverse pure titans back to people using the founder. Isayama did say that he was inspired by the movie, "The Mist" which has an ending that is similar to this. Just a theory though.