Hi, FTOS is what you want to move to as it is standardizing the OS across all product lines, rather than the S series having its own slightly different OS. [URL]   The S25N should be able to have 8.4.2.7 [URL]    
I am looking at this page [URL] And it is unclear to me what the latest firmware available for this platform is. Please help me understand what this means:  SFTOS to FTOS Migration Advisory:  Migrating from supported SFTOS release versions to FTOS Release 7.8.1.0, 7.7.1.2 or later requires upgrading first to FTOS 7.7.1.1. For example: SFTOS 2.5.3.2 --> FTOS 7.7.1.1 --> FTOS 7.7.1.x or FTOS 7.8.1.0   See the FTOS 7.7.1.1 download link below for instructions on migrating from SFTOS to FTOS 7.7.1.1.    I see that SFTOS 8.4.2 will go End of Maintenance in Nov 2014, and End of Support June 2015.  This seems to indicate that the SFTOS branch of code is being discontinued, and in order to move forward with this hardware I will need to migrate to FTOS.  When that migration is complete then can I assume that my target OS will be 8.3.3 or 8.3.5? And there is this: Please click to convert from  FTOS 7.7.1.0 to SFTOS. Which yields instructions to convert from FTOS to SFTOS. If SFTOS is being discontinued, why would I wish to use it?  Please help me clear up this confusion.
Force10 S25N - what is the latest firmware release?