I would hope that they change the combat system. Using die rolls instead but this time showing hits and dodges and misses graphically (instead of through sound like in Morrowind).
Or something like Mount and Blade's system with more focus on stats.
Oblivion's way of hitting everything as long as you aim at it was a pretty terrible system. If my orc can't shoot a bow to save his life, he shouldn't be able to hit everything just because I've got good twitch skills. Same concept as the lockpicking mini game basically, which rendered lock picking entirely useless since I could open any lock even if my security skill was only 5.
I agree, in Oblivion none of my characters took security or speechcraft as skill because they were pointless. Contrary to Morrowind, were nearly all my characters had security, or alteration.
I think you character's skill should be way more important. For something like bows, if my character has a skill of 5 it should be extremely hard to hit the target, have shots that fall short, or go over or way wide. And for melee weapons, if my char. has low skill, make him swing poorly, miss frequently, have opponent easily dodge or block my attacks. And if I do land a blow it should be a weak blow. And on the flip side of that, as my character develops higher skill in, say, blunt, let him land punishing blows, disarm or dismember his opponent.
I expect the combat in Skyrim to be similar to Oblivion, but I'd like it, and all other skills, to be much more dependent on the skill level and not the player's skill. I wouldn't mind seeing some tweeks to the system, and the perks. A master swordsman should be able to disarm more frequently, relative to the opponent's skill. And maybe some combination perks, ie: expert/master blade skill AND expert/master sneak skill unlocks the ability to to a critical dagger strike, mortally wounding or instantly killing the enemy...