TBH, having watched "Turn Left", "The Stolen Earth", "Journey's End" and "The End of Time" all in one go yesterday I think it will benefit the show for Moffat to move away from some of the bombast and back references that RTD seems wedded to, particularly in the series' 'finales'.
Two years in a row we've had cameos from Martha, Rose, Jackie, Mickey, Sarah-Jane, Luke and Captain Jack, and whilst she was integral last time around, this year Donna was kind of redundant. Though it's kind of fun, and while I appreciate RTD's idea about providing some kind of emotional closure to the Tennant era, it does smell slightly of nerd-pleasing 'fan w*nk', as if, having thrown "everything but the kitchen sink" into the mix, he then can't resist adding the kitchen sink itself, just for completeness.
I think it's time to dial back on this kind of 'stunt' plotting before the show disappears up it's own ar*e in a frenzy of circular references to it's own recent continuity. A few carefully placed canonical nods are fine, and I can understand Moffat's desire to revisit River Song and the Statues (they are his characters after all), but one needs to do it sparingly and for good dramatic reasons, not simply because one can.