According to what I've learned, Buddha Shakyamuni, Guru Rinpoche Padmasambhava, and Je Tsong-Khapa are all 'emanations' of Amitabha (Padma Family); and the Dzogchen Master Longchenpa Rabjampa wrote that Buddha Shakyamuni himself attained Illumination eons ago as well.
As for what this implies regarding Pure Land Buddhism, perhaps someone with more knowledge on Pure Land can explain.
Maybe this helps (also has a link to Dharmawheel threads):http://www.google.com/search?q=Shakyamu ... TF-8&hl=en
I was listening to a webcast recently, and Namkhai Norbu Rinpoche said that Garab Dorje is an emanation of Shakyamuni Buddha. This stuff is confusing