Knowing how zos loves to squeeze as much money out before this game fizzles out due to lack of innovation it will be separated, I for one stopped playing as there is no end game content, there is but you could do it all in a single day, upgrading to yellow armor or legendary armor is a joke and easy as all hell to do. My problems is no innovation, lack of being consistent, bad servers, just to name a few.
Aeonhack - AD Stamina Nightblade - 5 Star General
CP1200
Creator and user of "Questionable" addons and game mechanics.
Not sure about illambris or shadowrend (it is shadowrend the other pack coming out right?), but looking at datamined images of the upcoming Iceheart, Troll King and Grothdar packs, it would appear that there are individual packages and a set package (set may not be the correct term.... all-in-one-package?)
Edit: after reading the July CS overview again, I would think that there would be both a single all-in-one package and separate packages
Last I checked (briefly) on the PTS you can preview the Grothdar items and they can be purchased as a full set or individual items. What you can not do is buy a 2 handed "Maul / War Axe / Greatsword Style" and have it work on 1 hand maces/ axes/ or swords, respectively. Each weapon regardless of 1 hand or 2 hand, has its own style that needs to be purchased.
All of that aside, I am really looking forward to purchasing the Illambris as a set, and I pray to the divine that Illambris was not replaced by Grothdar or that Grothdar does not come out before Illambris. I want it now.