I think its quite obvious about the type of things its
not going to be :
- Higher Item Level(s)
- Removing the Shared Lockout
- 15man Raid Size
Higher Item Levels and Removing the Shared Lockout (between 10 and 25) just causes people to feel that it is required to run both if they want to play competitively (which alot of people do).
15man Raid Size will just generally annoy everyone. 10man guilds will have to recruit more players. 25man guilds will have to lose players.
I personally hope that the difference is something more "appealing" rather than mandatory. But also not something gimmicky like crappy Bags which give Flasks / Potions.
I think to begin with they should try and improve some of the Game's Interface.
For example, the In-Game Calender could do with improving. Being able to select role(s) when signing up is one small step forward to helping Raid Leaders and Officers with organizing raids.
Not just for current content either. The option to invite RealID friends through the In-Game Calender to an event.
Other than organizing raids, officers also have issues with recruiting players for 25man. Sometimes this means having to search on different realms for new decent recruits, however not everyone can afford to Realm Transfer willy-nilly. I think it would be nice to allow players to raid content cross-realm (currently you cannot raid current content cross-realm. I feel this should be removed).