So they may do a horse and his boy, or will it be another one. A horse and his boy happens, from what I recall from reading it back in the early 80's, during the reign of the 4 kids from the first book, actually during the latter part of the 1st book, but before they chase after the white stag or whatever it was they were chasing. Must have been shocking for them to be older teens or adults then, poof you're back to your old age again.
One bit of narnia history that is pretty unknown is the 900 years that happens from the end of The Magician's Nephew and the white witch returning in the year 900 I think it was, when she returned. Between the first & 2nd book some main events are known.