Anyway, it seems to me that now that we know Hand-to-Hand is out (I am somewhat surprised about this) we can with confidence determine the 18 skills.
Take the 21 skills in Oblivion. Now remove Acrobatics, Athletics, and Hand-to-Hand. Replace Mysticism with Enchanting. (And there are other little things like replacing Blade & Blunt with One-Handed & Two-Handed, and replacing Armourer with Smithing).
It sounds like the 18 skills are:
One-Handed
Two-Handed
Shield
Heavy Armour
Smithing
Enchanting
Conjuration
Destruction
Alteration
Restoration
Illusion
Alchemy
Archery
Sneak
Security
Light Armour
Speechcraft
Mercantile
The only way that this isn't the skill set, it seems to me, is if (i) there's a new skill, or (ii) a skill returning from an earlier game. I can't think of any plausible candidates for (ii). I haven't really thought about (i) so much. In the past some people have mentioned Dual-Wielding being a skill. (I previously thought that was implausible. Now my confidence has been raised. Combat, so far, has only 5 skills. If there is a new skill, it seems more likely that it should be a combat skill, to balance it with magic and stealth).
Thought?