I think they will keep the same structure as current. 16GB, 64GB and 128GB. This is only an "S" update. It would be nice for the base model to be 32GB but as Apple would lose out on a lot of sales for the mid-tier phone because 32GB would be enough storage for the majority. So, really from a financial standpoint Apple will likely not change because it basically forces the upsell for $100 more.