As far as I know, the Expedition moves to the new platform a year after the F150 is released. This is a gap filler until then.
Sales in the segment have been falling though. In the US, the Expedition sold 163K in 2002, 38k last year. The Suburban sold 151k in 2002 and last year it was down to 51K. The Sequoia dropped from 70k to 13k.