It may be pricey but I can't see why you couldn't get the second row bench installed after the fact. I bet the transition through the dealership will be close to $2000 since they list the seat frames alone for $220 ea. Probably too soon but you might want to start looking for them through a junkyard. I want a split 3rd row (wouldn't doubt if they put them in the 06'). Some one may even come out with an aftermaket...I've seen them advertise adding 3rd row seats for SUV's like the xterra..
I just re-read your post. No the second row bench won't go in the third row. It's much thicker and more hardware than the third row.