time between new model release and used values falling?

[sneaky]

just wondering how long the turn around is between a 'new' model getting released and the 'previous' model dropping price?

a bit of background. i'm looking at purchasing a FG xr6t, with luxury pack, some time this year. i was planning on buying a euro4 (mid 2010) model later in the year but the wife has given the green light for me to buy sooner rather than later . the budget won't stretch to a 2010 model at the moment but i could buy a 2009 model with the luxury pack.

now here is the dilemma - will the FG series 2 release lower the prices of the FG1 any time soon? does the new model almost instantly lower the price on series 1, or will the prices only start to fall when used series 2 fg's hit the market?

reason behind this is back in the day i did a silly thing and bought a used car (commodore) and within a month a new model got released and killed the resale on the car i had.. so six months later i sold the car for a massive loss ($18k purchase, $12k sale)

so any advice/info/stories/experiences would be good.

thanks
-tim