It looks like 256GB will be the base storage starting point. I would be happy if Apple introduce a 1.5TB/2TB iPhone.
This is actually great for me, even if there's a price increase. I only need 256GB, and if you ever need to trade-in or sell your phone, you get the most money for the base model. Apple doesn't increase trade-in if you have more storage, and you don't recoup as much of your cost when you sell your phone.