Is there a reference to JP II saying that the Luminous Mysteries were only to be used for a single year?
Well, they were always optional, a sign they weren't meant to be used forever or to be a part of the rosary. I mean, how could something be optional? The rosary is one prayer. You don't see optional psalms
I believe, however, that to bring out fully the Christological depth of the Rosary it would be suitable to make an addition to the traditional pattern which, while left to the freedom of individuals and communities, could broaden it to include the mysteries of Christ's public ministry between his Baptism and his Passion.
It is no more than a suggestion for personal variation. Anyone can add to the rosary, as long as they don't change its basic form. This is just a suggestion for a particular alteration for private devotion.
Consequently, for the Rosary to become more fully a “compendium of the Gospel”, it is fitting to add, following reflection on the Incarnation and the hidden life of Christ (the joyful mysteries) and before focusing on the sufferings of his Passion (the sorrowful mysteries) and the triumph of his Resurrection (the glorious mysteries), a meditation on certain particularly significant moments in his public ministry (the mysteries of light). This addition of these new mysteries, without prejudice to any essential aspect of the prayer's traditional format, is meant to give it fresh life and to enkindle renewed interest in the Rosary's place within Christian spirituality as a true doorway to the depths of the Heart of Christ, ocean of joy and of light, of suffering and of glory.
It isn't meant to be changing the rosary as a whole (unless he is suggesting that a novelty is important for renewing interest, which many may claim, but I think these mysteries are just a personal suggestion for private devotion).