Sony just filled the registration for two new models of PS3/4 :
The PS4 has just been launched a few months ago, but Sony might already be planning to launch a new model of its new console. The manufacturer filed for the registration of two new “Computer Entertainment Systems” with the Ministry of Communications and Information Technology of the Republic of Indonesia.
The filing, listed on the official website of the Directorate of General Resources and Equipment of Post and Information Technology, bears the model number CUH-1106A. This seems to indicate an evolution of the console, but not a radical redesign like the passage from the PS3 slim to the super slim, for instance, which is normally indicated by an incremental change of the first number of the code (the slim was launched with the model number CECH-2001A, while the super slim started with CECH-4001A).
source www.dualshockers.com/2014/05/21/new-ps4-and-ps3-models-possibly-outed-by-certification-request-filed-by-sony
They also announced a new manufacturing process for cell (smaller and more efficient) :
@anandshimpi On a related note, the word is that there's a new super slim hardware revision with a 28nm RSX... 22nm Cell next year.
— Digital Foundry (@digitalfoundry) June 29, 2013
This was to be expected since, unlike Microsoft, Sony hasn't released a new PS3 model to accompagny the next gen console.
This means that while a new PS4 model is unlikely, the announcment about a Cell reduced in size could mean that a slimer PS3 with a new design to match the PS4's, and eventually the new interface, could be released.
It is also possible that, the PS4 not being backward compatible and the PSNow service not being fully ready, Sony allows the two consoles to sit side by side and be connected?