I am not sure about you auditioning for Aravis, as a Calormene you would have to have darker skin also, I would go for it anyway because they have changed some other things about the movies. they might decide that you would make a great Aravis.
As for Horse and his boy, I had heard on a different Narnia site that they might film it last.
I think they will film it (even if Adamson is not the director) because it is a very popular book.
If they don't I will sue Disney and Walden Media, not Adamson.