I really can't see them not being involved in someway. What's the point in an anniversary if you don't look back at everything that got you to that point? I know Moffat has said that he wants it to be about looking forward, but Rule:1 will hopefully apply.
"The universe has to move forward. Pain and loss, they define us as much as happiness or love. Whether it's a world, or a relationship...everything has its time. And everything ends."-Elizabeth Sladen: RIP.