However, considering the rumors that we may see the First Doctor yet again at Christmas, there might be a chance that Steven Moffat and might be tying up his tenure as Doctor Who’s showrunner with a trip to the vault of series history, finally resolving what happened with The Doctor’s granddaughter and former companion.
Seeing as “The Husbands of River Song” is probably still fresh in his mind, The Doctor may have specifically promised his beloved that he’d protect the vault.
If you look at The Doctor’s desk in “The Pilot,” there are two photos he continually talks to, and they’re of the two most important people in his life: River, his most recent wife, and Susan, his granddaughter from the earliest era of the show’s history.