On March 30th Trion announced that they would like an extra week to work on this month's Patch 1.8 before it is released. Phase 5 of the Carnival of the Ascended had its share of troubles with the repeatable War Trophies quest not updating the phase goal and will be extended by a week to fill in this gap.
The reality is that we wanted a little more time to get Update 1.8 ready for prime time and, at the same time, wanted to make sure everyone could enjoy all parts of Phase 5 as well.
This allows us to hit two birds with one stone - we know the update has tons of awesome stuff in it, but we still won't release it until we're ready. It's why we rarely give more than a few days notice about the release of our updates anyways, the World Events just happened to put a giant neon sign on our target dates this time around.
As we've said though - we're not afraid to try new things, hit or miss we're always working to make the game interesting and fun in different ways!
Source: Rift Forums