Same concept applies to the second port for the SSD: while there might not be a bracket to hold a drive in place unless you order a Fusion Drive option, the port should at least be there and be usable. Will have to wait and see.
It has been suggested that the SSD will likely be of the sort used in the laptops: a "blade" with an edge connector, so standard form factor third party SSDs might not be an option, although perhaps the blades sold by places like OWC might be.