My predictions:
Furio – ain’t comin’ back. Too many viewers want to see him come back, and David Chase never brings back characters that viewers want to see again. (Same goes for Melfi’s rapist, The Big Russian, etc.)
If Chase does give in to fan pressure and brings back the Big Russian, expect it to be some kind of unexpected throwaway – like, Christopher sees this big drunken bum in the gutter, does a double take, then shrugs and keeps walking. What we WON’T see is some shocking reappearance a la Jason Voorhees, i.e. Paulie shuts the medicine cabinet door and the Russian is RIGHT THERE BEHIND HIM!!!
Svetlana – almost certain to make an appearance somewhere down the line. BTW, Janice never did get her mother’s records back.
Tony B’s kids – ain’t comin’ back. What would they have to do?
Devin – back as AJ’s GF, might have a bigger role this season, perhaps will be instrumental in leading AJ to more mob-related activities. Who knows for sure? Frankly, I’m hoping that AJ’s other friend (played by Paul Dano) gets a much bigger role this time round.
Finn – Meadow goes through boyfriends faster than Tony goes through gabagool (sp?) so she’ll set herself up with a new squeeze and Finn will be forgotten. Hopefully the Gay Vito subplot will remain forgotten as well – never did buy that twist.
Feech – Would LOVE to see Robert Loggia make a return! However, I can’t see how they’d make that work, and his obstinate character would conflict with Tony in exactly the same way as season five, so there’s really nothing new for him to do.
Frank Sinatra, Jr./David Lee Roth – very unlikely, but we’re sure to see a few new cameos this year.
Paulie’s Mom – as mentioned before, she’ll probably just die, providing a major turning point in Paulie’s character arc. Speaking of Paulie, I wonder if he’ll be wracked with guilt for whacking that old lady last year? Or is he too hard core to even care?
Tony’s other sister – Barbara only seems to show up at reunions and other family functions, so the same will hold true this year. She’s another character I’d like to see get explored more deeply.
Assemblyman what-his-name (the one who slept with Tony’s ex-GF and got beaten up by Tony as a result)…is he still around? I’d like to see him again.
Will Tony hook up with Charmaine? – not a chance.
If so, what will Artie Bucco do? – Artie might start getting deeper into mob activites, but his one little foray into the business ended very badly last year, so that will probably dissuade him from it.
Regarding Livia’s house…yes, it was sold in season one and magically unsold in S2; however, I have no problem accepting that the original offer fell through and they never got around to selling it again. My mother just sold her house after having THREE previous offers fall through at the last moment (including one that went all the way to escrow!) so yeah, it could definitely happen that way. (I keep telling her she’s worshipping the wrong God and each week makes God madder and madder…)
Who will be Christopher’s next squeeze? – I dunno…Meadow, perhaps? 
Will Angie Bonpensiero learn the truth about Pussy? – As previously stated, she already knows or strongly suspects what really happened.
What will be Uncle Junior’s next big move? – pissing in his Depends, taking experimental Alzheimer drugs, and so forth.
Will Meadow get a job at the Bing? – With that ass?? Are you joking? 
As for the Tony/Johnny Sack situation, remember that Johnny Sack went to jail at the end of season five, so whatever business he tries to stick his beak into will be a lot more limited this year.