Never fear, fellow WoW players, it's Community Manager Crithto to the rescue in the forums today, with a long and detailed post going over exactly how (for the moment, at least) the developers are designing gear for Warlords of Draenor. This is a fascinating insight into the thought process behind the design, which strikes me as rather flowchart-like, in a good way. There are, in a sense, stat tiers within the design of each piece, meant to make our gear both more flexible and more customizable.
Gear is divided into two categories: armor (head, shoulders, chest, legs, gloves, belt, boots, and bracers) and non-armor (weapons, rings, cloak, necklace, and trinkets). In general, armor pieces will have primary stats, and non-armor pieces will not, with the exception of weapons. As far as stats go, there are three types: primary, secondary, and tertiary. Primary stats can be one of three things: Strength, Agility, or Intellect. A gear piece's primary stat will change depending on your class and spec. In addition, all armor pieces will possess some value of Stamina and Armor, and that will not change depending on your stat.
Secondary stats will not change based on your class or spec--they are fixed on an item. Secondary stats include things like Haste, Crit, Mastery, Spirit, and Bonus Armor. In addition, Blizzard is exploring new possibilities for secondary stats, for example, things like Readiness, Amplify, and Multi-Strike. These are still in development, and nothing is yet certain. Armor pieces (as listed above) will not possess Spirit or Bonus Armor. Non-armor pieces, however, can.