"This was a temporary assignment"

[Photon]

Sisko said this to Kassidy in Prenumbra. So if things went to SF plan, Sisko would have gotten Bajor in and would have left to another command, right?

 

[Jono]

Any assignment would be temporary since Starfleet can reassign its officers to different commands. Plus Sisko at the beginning had no intention of staying in the service for much longer.

 

[erastus25]

Any assignment would be temporary since Starfleet can reassign its officers to different commands. Plus Sisko at the beginning had no intention of staying in the service for much longer.

You're right, any assignment in starfleet is temporary so I don't think that's what Sisko meant. There's no point in saying that if it's true for all the officers. More likely he was referring to the fact that he didn't want the command at all and planned to quickly move on, as you also note.