According to mmo-champion, the Icecrown Citadel raid buff has been increased from +20% to +25% for damage, healing and health. Blizzard has again been true to their four week cycle on the ICC buff. Only 159 guilds worldwide having completed the Lich King 25 Heroic to date - with this extra 5%, we should see this number increase somewhat over the coming weeks.
At this rate, we can expect the next +30% ICC buff to be active on Jul 20.
ZARHYM: We have increased the potency of the Strength of Wrynn and Hellscream's Warsong buffs in Icecrown Citadel by an additional 5%. These buffs now increase total health, healing done and damage dealt by 25%. In addition, the number of attempts allotted for all final bosses on Heroic difficulty has been increased to 55.
Update: Later correction from Zarhym - the number of pooled heroic attempts remains at 50.