Tom - Tom basically has 2 alliances that he can go with at the moment: The Four (Tom, Ian, Katie, Steph) or The Five (Tom, Ian, Katie, Gregg, Jenn). Tom would be smart to go with The Four, since it is possible to pull off now that there is seven left. Plus, Gregg is already plotting against him. Tom is vulnerable simply because he is the leader of Koror. Any "revolution" in the tribe will begin with the king's head getting lopped off. At Four, Tom could then stick to his Core Three alliance of him, Ian, and Katie and get rid of Steph. At that point, it's either up to Tom to win final immunity or Ian (I believe Ian will take Tom to F2 if it comes down to it). If Tom makes it to the Final Three, he is in the finals and a good bet to win.
Ian - Ian just has to ride Tom's coattails, going along for the ride to the Final Four mentioned above. At that point, Ian can either drop Steph or drop Tom (not Katie!). Either way he goes, he needs to win the final immunity and bring in Katie (but I doubt he will); I don't think he could win against Tom or Steph. But if it came down to those two, he'd have a better chance against Steph. To summarize: get to the F3 with Tom and Katie. Either win final immunity and take Katie, or if by the grace of god Katie wins, convince her to take him to the F2.
Katie - Katie has to be sitting pretty right now. She has 3 potential alliances: The Four, The Five, and The Girls (her, Jenn, Steph, and Caryn). Since the third alliance doesn't seem likely, I'd advise Katie to stick with The Five, getting rid of her biggest threat Steph early. Then she should team up with Jenn and Ian and get rid of Tom first and then Gregg. At that point, she can rest assured that Ian will take her to the F2 if he wins final immunity. Jenn might also take her to the F2. Really, anyone in there right mind will take Katie to the F2. As for her chances of actually winning...
Steph - Steph, moreso than anyone else left on the island, has to make some big moves in order to advance. Her best bet would be to drop this Girls alliance and approach Gregg about making a New Four alliance of them two, Jenn, and Caryn. Steph already knows Gregg was going to break away from The Five once it got down to 7 people, thanks to Coby's big mouth. I'm sure Gregg would take her offer. I'd take out Tom first, and then Katie. At Five, Steph should take the final outsider, Ian, and ask him to vote with her and Caryn against Gregg and Jenn. Then at three, she should be able to win the final immunity and then take Caryn. A guaranteed win. To summarize: team up with Gregg, Jenn, and Caryn to vote out Tom and Katie. At five, team up with Ian and Caryn to vote out Gregg and Jenn. At three, win the final immunity and take Caryn to the F2.
Gregg - It's do or die time for Gregg. There are only 7 people left and he needs to turn on his Five alliance next in order to advance to the Final Four. He should team up with Steph, Jenn, and Caryn for a New Four alliance. Do this first and then convince Caryn to vote out Steph at Four. At three, Gregg can win final immunity and take Caryn. In fact, he could take Jenn and still likely win. Jenn would likely take Gregg if she won final immunity, so if he can make Final Three with those two, then he has a good chance of going to the very end and winning. Another option: Gregg can vote out Tom and Ian with his New Four alliance, and then recruit Katie to join him and Jenn to take out Caryn and Steph. The Final Three rule for him still applies, only this time if Katie wins she could take Caryn to the final with her. I predict easy wins against either Caryn, Jenn, or Katie.
Jenn - Jenn is lucky to be protected by Gregg. At this point, she should follow the plan I proposed for Gregg above, the only difference is that she would have to win final immunity and take Caryn/Katie to the final instead of her boytoy.
Caryn - Caryn's situation is interesting. She has nothing to offer anyone except her vote. But at seven, her vote can easily mean a big difference to the warring factions. She should approach whomever and try to negotiate a Final Four deal. She can go to Tom, Ian, Katie (not a good choice) or do The Girls alliance (not likely), or she can convince Gregg and Jenn to team up with her and Steph. The only problem with that is that she can't really beat any of them in front of the jury. Really, she should just find some way to take Katie to the F2 with her, but that scenario seems highly unlikely. Her next best bet would be Jenn, so, if I was Caryn, I'd team up with Gregg, Jenn, and Steph now, dump Steph at Four, win final immunity and take Jenn to the F2 and hope for the best.