I don’t see The Child and Ahsoka both being alive at the end of this series.
I can see them killing off Ahsoka, though I don’t think its necessarily guaranteed. However, I definitely do not think they’ll kill of the child. Considering how popular it is, and how upset people got from it simply being punched by a stormtrooper, I highly doubt they’ll be that bold. I think they’ll find some excuse to keep it away from the main events of the galaxy, probably reuniting it with Yoda’s Species which has stayed hidden so far in SW canon, or something similar.
I hadn’t thought about that, but now that I think about it, Filoni kind of already did that with the Lasats in Rebels. So it wouldn’t be unprecedented.
Plus, it would be pretty hard to kill off Ahsoka, considering that she’s now Death Proof.