What I meant by streaming, is streaming of textures. In games like Rage the pop-in is greatly reduced if you put a SSD in.
With PS3 Rage was a rare example of a game benefiting by having a SSD, cause most games only installed a small portion of the game to the HDD and still read from the bluray disk.
Found this on the PS4's blu-ray
The read-only optical drive reads Blu-ray discs at 6x constant angular velocity for a maximum read speed of 27 MB/s a significant upgrade from the PS3's 2x speeds that were capped at 9MB/s. To further enhance optical drive performance, the PS4 features a hardware on-the-fly zlib decompression module (a special piece of hardware used to quickly decompress the data on the Blu-Ray disc, which has been compressed to save space and bandwidth), allowing for greater effective bandwidth, whilst at the same time, the console continuously caches data onto its hard disk, even buffering unread data when a game isn't actively accessing the optical drive, forming part of Sony's PlayGo strategy.