Almost every Luke, Han, Leia, Chewbacca and somewhat recognizeable classic "B character" has been re-offered by Hasbro in this OTC appreciation year.
I think we'll yet see these figures re-offered again:
Death Star Trooper - available limited in 1998, in Accessory Packs in 2002. Still in demand most likely - since he's an army builder. Could be reposed, or paint deco'd in a grey uniform.
Han Solo Hoth Gear - the blue and brown coat Saga 2003 figure will be back again. A superior figure, it never pegwarmed, it's a main character, and most of the other Han Solo figures are available, plus Hoth has been recently promoted in a lot of ways. Thus I bet Saga Han Hoth will be back OTC style.
4-LOM - almost all the other Bounty Hunters are available again, and 4-LOM last graced shelves in 1997. Bounty Hunters are popular in general, so I bet the already pretty decent 4-LOM figure will be re-issued as it is.
Zuckuss - last seen in limited amounts in 1998, a re-release with no update of this very decent Zuckuss bounty hunter figure would not surprise me in the slightest.
AT-AT Driver - already rumored, this Imperial specialist is always popular and was never available on the pegs in the normal sense. A 1998 Fan Club Exclusive since retailers cancelled orders of his shipping case in anticipation of Episode One cases, the only other way to get the AT-AT Driver was with the AT-AT vehicle, also available back in 1998, and sort of made an opportunity on clearance in 1999/2000. I'd expect the figure will be just a re-release, or they'll use the current TIE Pilot with the added articulation to update him (if they bother).
AT-AT Commander - only available with the AT-AT vehicle, a General Veers figure is rumored, so this figure will hopefully be updated and given a lot of cool features.
Princess Leia Boussh Disguise - last available in 1997, she's long overdue. A great early figure, I'd guess she'll just be a re-release, but there's no telling. Another Jabba's Palace TRU 5-pack might include this Leia with other older Jabba figures like Tessek, Ree-Yees, Pote Snitkin, and so forth. I'm not sure an updated Leia Boussh is warrented. A re-release is though - at the very least.
Han Solo Endor - a coated one wearing his camaouflage duster hasn't seen release since 1997. A cloth cloaked one is in order, perhaps updated with brown pants and lots of articulation.
Princess Leia Endor Gear - this figure is in bad need of a decent upgrade. I'd expect to see it, if not in 2004, than by 2006 or some anniversary date either for SW, or ROTJ. The cloth poncho, working holster, new lower torso mold, removeable helmet, etc. would all be expected of a decent Leia
Emperor Palpatine - the last figure released that came out in the 2003 Saga line was pretty fan-hated, from what I could gather. I'm biased of course. A super articulated Palpatine with a cloth cloak, poseable lightning that can "get" Darth Vader Emperor's Warth while carrying him, might just do the trick. Palpatine is surprisingly a main character from ROTJ not represented by anything in the OTC collection. I bet he'll be in a late release for 2004 not yet announced. Maybe Comic Con or September/October Pre-Toy Fair will reveal him. This figure could be released as Darth Sidious though. We'll eventually see Palpatine or learn what Hasbro's been waiting for.
Ree-Yees - a main recognizeable character from Jabba's Palace and a star in the vintage line as well as a 1998 hard-to-find, many more got Ree-Yees, released with the '98 carded Death Star Trooper, as a Fan Club Order, so I think he might do well hitting the stores as a regular line figure. Grans were recognizeable playing many roles in the prequels too, so it's possible Ree-Yees would be turned down for Senator Allein Teem, or Ask-Aak, Asks-Moe, or the Podracer Mohawnic. Any of the latter would be a welcome change actually, and help Hasbro catch up on their prequel senators and podracers.
Tessek - a POTJ masterpiece, the 2001 figure was never a pegwarmer, and many consider him a fine piece. Tessek is also one of the other staple Jabba characters that are really recognizeable. I'd gamble he'll be a straight re-release. However, Senator Tiikes (in red and a Separatist) should be well appreciated as a change for fans of Quarren characters. With repainting, we might just see both (hopefully).
Admiral Ackbar - once a pegwarmer in 1997, he's not been availble at retail since. He'll be back. Probably a re-release. They can't really improve on his decent previous mold.
Luke Stormtrooper - a classic version of Luke. It'd make sense that they re-offer this figure. Possibly in late 2004.
Han Stormtrooper - a supposed promise made to fans that Han would remain specially packaged - as the Fruit Loops mail-away or the 3-pack figure, would logically be renigged on. Why? New fans collecting for the first time will want a main character in a key costume. I could see a SA Han Trooper done as part of another wave of OTC vintage style figures, so as they keep the promise (since he's not in the regular line) and they make more money off selling him. The original Fruit Loops one is between $10 and $30 on e-Bay the last I heard, so Hasbro could get away with an OTC vintage edition.
Han Carbonite - this figure begs for an Ultra Version. Last available in 1999 as part of the Jabba's Palace diorama, a predecessor dates back to 1996. Han is in bad need of an update here, as well as a version that is still frozen and hangs on Jabba's wall. Han Carb could be an exciting updated figure if Hasbro does it right.
Luke Endor - removeable poncho, removeable helmet, lightsaber that hangs on the utility belt - probably no gun in holster (while the Kenner figure had this, Luke as a Jedi didn't use a gun so far as I remember the movie accurately). But Luke begs for an update and they could do a nice job on a new version of Luke in this style.
That's about it. But most of the major character you absolutely, essentially need to play Star Wars, are going to be available this year.
In fact, the original vintage line of 102 figures made by Kenner covered almost every major character we needed in one form or another, and Hasbro has 36 of the most well-known either shipping or getting ready to.
Of those modern figures that were never-made-before, Grand Moff Tarkin, perhaps in an updated version, is the most likely we'd see again. Last available in 1997, an updated version would be more likely than a re-released one.