The zero sum game in Zero Sum Game
could be a reference to the Federation/Pact standoff and/or the Breen having stolen the Slipstream hence the spec ops mission to destroy it.
The Bashir/Sarina relationship will be interesting to see I think. I always liked her character and thought that she'd be a great fit for the good Doctor. Ezri has grown so much as a person these past years, I think getting back into it with Julian would be a step backwards. That said, I'm not 100% opposed to it if done right... and with David Mack on the case I can say for sure that it'll be done right no matter the relationship outcomes (at least IMO - link back to the Mack Appreciation Thread http://trekbbs.com/showthread.php?t=109712