to a question about the number of SiN episodes being planned, Ritual's Michael Russell let us know that a patch is in the works for the original SiN. It's been given a higher priority than SiN: Source, currently on hold until completion of the patch. There's no word yet on what changes have been made.
Regarding the length of SiN Episodes, ParadoX said
that 9 episodes have been planned. Emergence is the only episode in active production and episode two is in preproduction.
An update from Michael:
<blockquote>To clarify, SiN 1.12 is the Steam version of SiN. Aside from some minor asset tweaks, a new sound system, a new video playback system, minor modifications to the network protocol and support for Steam, there are no additional changes from SiN 1.11.</blockquote>