When iPhones reached 128GB last year, I would easily bet that Apple would abandon the version of 16 GB. It was much more obvious a 32GB / 64GB / 128GB line than the current one, 16GB / 64GB / 128GB. But this is what Apple did, and it was widely criticized for it.
Now the M.I.C. Gadget claims to have obtained information from sources at Foxconn who claim to have seen no reference to a 16GB model on the iPhones' production lines that will be released soon. That is, it may be that this year we will have devices with a minimum of 32GB of capacity.
What can also happen to the "iPhones 6s and 6s Plus" have a minimum of 32GB, and Apple will launch an "iPhone 6c" this one with 16GB. It is worth noting that, with the new iPod touch, Apple preferred to offer them in four (!) Versions: 16GB, 32GB, 64GB and 128GB.
The expectation that the launch schedule will follow that of the past years, so we will probably have a keynote occurring maybe on the 8th or 15th of September.