If Gillespie is picked he'll go into the series having not played a real Test since his last 3 against England.
Having said that, it shouldn't really matter - he's bowled superbly in the domestic-standard games - Pura Cup, Bangladesh, and in all likelihood Championship too. I'll be very surprised (and, being a Yorkshire fan, disappointed) if he doesn't do very well this season.
Let's face it... none have done anything to be left-out - Australia don't have enough good batsmen to score runs against a full-strength, firing English seam-attack - why not give yourself the best chance of hitting back... and Warne, Lee and Gillespie all have some pretensions with the bat, while clearly none are all-rounders.
The only Australian batsmen I'd back for success this winter are Ponting and Hussey. Hoepfully England will end Martyn's career as we kick-started it.
RIP Fardin Qayyumi (AKA "cricket player"; "Bob"), 1/11/1990-15/4/2006