Hard to say.
Geelong are more likely to regress than improve, and already have almost all their players in their prime. Inasmuch as they can improve they need to get more pace around the midfield and hope that Hawkins continues to develop as a big forward target in the top side. The physical and mental toll of sustaining a winning record like Geelong's has bitten hard at those sides who have maintained similar records, however, and will almost certainly do the same to Geelong at some point. Most likely (as Carlton 1996 & Essendon 2001 did before them) Geelong will start well and hit the wall midseason.
That said, other teams have responded well to GF defeat and the Cats could surprise and extend their unlikely run into another year.
Unlike Geelong, Hawthorn has most of its players yet to enter their prime and - given it is five years behind Geelong in development terms - would appear to have a lot of improvement yet. Where the side needs to firm-up is in the ruck and with an extra KPP defender. If the club can improve the goal kicking accuracy of Messers Franklin & Roughead then it will be very scary indeed for the rest of the competition (This is all that stopped Franklin taking the goalkicking record and Roughead finishing second behind him with a ton this season). The unknown is how susceptible the side will be to a hangover.
And then there's the other sides closing the gap on both...
Its improbable that both sides will back up in the 2009 decider and don't be totally surprised if both miss.
No, its definitely not a two-horse race.