I'm pretty sure I have guessed which skills have been removed (or combined):
MYSTICISM: DELETED.
ENCHANT AND CRAFTING ADDED.
ACROBATICS AND ATHLETICS HAVE BEEN COMBINED (PLACED UNDER STEALTH)
SPEECHCRAFT AND MERCHANTILE COMBINED.
THE MAGIC SKILLS: DESTRUCTION, ALTERATION, ILLUSION, RESTORATION, CONJURATION, ENCHANT.
THE FIGHTING SKILLS: ONE-HANDED, TWO-HANDED, SMITHING, BLOCK, ARMOR (IN TOTAL), HAND-TO-HAND.
THE STEALTH SKILLS: SNEAK, LOCKPICKING, MERCHANTILE/SPEECHCRAFT, ACROBATICS/ATHLETICS, ALCHEMY, MARKSMAN.
This is just a guess...
Do any of you think I'm right...
I guessed the 18 skills a few days ago and wrote them down in a text file, and I made the exact same guesses as you.
Since we know alchemy is in and that both Combat, Stealth and Magic will have 6 skills each, we can safely put alchemy under stealth.
Mercantile and speechcraft make sense to combine, as do atheltics and acrobatics, though not as much as the former (I'm good at making people like me, but I cant get them to pay a high price for my wares? Or good at selling high and buying low, but hated by everyone? Combine them immediately!
).
Light and Heavy armor can be combined as well, and instead being strenghtened by different Armor perks.
I think all of this makes sense.
Actually, looking back over this, I imagine sneak and lockpick will be combined into some kind of generic "burglary" skill, but I don't see them combining light and heavy armour any time soon. Too different from one another.
Heavy and light armors are just differently sized armors. They both serve the same purpose: To shield the wearer from damage, with the difference being that light armor sacrifices protection for mobility.
And if a sword, an axe and a mace can be strenghtened by the same skill, I don't see why two different armor types can't.