In the US, I say Spring 2005 for the 997 coupe as an early MY 2006 , fall 2005 for the '06 cab and spring 2006 for an early '07 997 TT.
I reason they will want to sell the current 996 platform in the C4S Cab, TT cab, GT3, possible Speedster and possible Turbo S into a shortened second model year ( MY 2005 ).
They realy DO need to bring the new Boxster first ( MY 2005 ) as that model is realy dragging them down right now . Also a way to " beta" new systems on the entry level car before the 911's revision.