I'm sure I'm the last one to be in the know about this, but I figured I'd post just in case.  In a lot of ways it seems the perfect solution for our way of raiding, though I can also see peeps missing out on gear because of it as well.  Anyway, from an apparently blue post I found copied over to curse.com:

[quote:599e9badd3]In the next patch a new feature will be become available that will give players the option to extend the instance lock, or instance ID of a raid or heroic dungeon. It will be possible to extend an instance lock more than once and each extension will grant an additional amount of time equal to the duration of the original instance lock. In other words, you'd gain 24-hours if you chose to extend the instance lock of a heroic dungeon, whereas you'd gain 7-days by extending the lock on Ulduar. Additionally, extending an instance lock is a choice that's solely up to each individual, and is not controlled by the group's party or raid leader. This new option is being added as a means to allow parties and raids to progress through an instance at their chosen pace, and should prove to be a useful option available when the patch is released.[/quote:599e9badd3]