A lot of people worried or concerned about itemization in D4. So here is some info that will hopefully shed some light on the topic!
RUNES AND RUNEWORDS
Runewords no longer work like D2, and no longer replace other item types. Instead Runes can be socketed into any items to give bonuses based on "condition" and "effects". So Runes have synergies together.
Examples of Condition Runes:
Amn*- When you freeze an enemy, activate the next socketed runes.
Vex*- When you use a healing potion, activate the next socketed rune.
Eth*- Every 3 seconds without moving, activate the next socketed rune
Eld*- When you are stunned or frozen, activate the next socketed rune.
Examples of Effect Runes:
Ko - When active, reduce a random skill cooldown by 15%.
Dol*- When active, gain 50% critical strike chance for 7 seconds.
Sol*- When active, gain a random shrine effect for 7 seconds.
Ist*- When active, your next thorns hit deals 30% more.
So, if you socket the condition rune Vex with effect rune Dol into an item, the effect would be: "When you use a healing potion, gain 50% critical strike chance for 7 seconds."
Runeword progression is being discussed, like being able to combine more than two Runes with each other.
Item Types and Quality
MAGIC
Magic items can have the highest individual affixes.
RARES
Rare items can have up to five affixes., And are usually better than*Magic*items.
LEGENDARY ITEMS
Legendary affixes have increased power on specific item types (e.g. a specific affix might have 33% increased power on an Amulet)
They modify skills in a similar way as seen in Diablo III
Hundreds of new Legendaries (different types: generic (good for every build), category-specific and skill-specific)
Class skills crossing over through Legendaries is being explored, but very limited and only on endgame items to keep class identity intact
Legendaries will not "rain from the sky" like in Diablo III.
SET ITEMS
Less powerful or equal to Legendaries (more introductory to the class or to live out a certain fantasy), which means that you will eventually graduate out of them. (This is a HUGE shift from D3, and more inspired from D2!!!)
UNIQUES
Unique items are back and will be quite powerful and desirable like D2 before LoD Runewords mostly replaced them!
Build-around items with completely fixed affixes
Heavily thematic and usually with class-specific powers.
Trading
Trading will not be completely open-ended. Items will either be tradeable, bind on trade, or bind on pickup. As with all features, this is subject to change. The developers think that the predominant source of items should be from killing monsters.
Gambling
Gambling will be an improved version of Gheed (Diablo II) and Kadala (Diablo III) and will act as a gold sink. The best items in the game will be available through Gambling, which will keep gold meaningful.
Crafting and Artisans
Crafting incorporates the world by slaying monsters or finding rare crafting materials at a specific location in the world. You will be able to create items; however, endgame will mostly revolve around item modification. The removal of items from sockets will come at a cost.
The Occultist
The Occultist lets you extract a Legendary affix from a*Legendary*item into a*Legendary Essence, destroying the item in the process.
The Legendary Essence can then either be implanted into another*Legendary*item, overriding its existing Legendary affix, or be implanted into a*Rare*item, upgrading it into a*Legendary*in the process.*"Uniques"*cannot be modified. These Legendary Essences can be stored and used at a later time.
Hope this answers some questions!






