Hard to say. I've gone ahead and bought the Kona an the new models are out in a month or so. I think the Specialized 2010 models are already out. A few things to consider -
When the new models come out - the older stock often goes on sale at lower prices. Though some shops are already reducing prices of remaining stock. However, there are reports that companies made less 2009 bikes because of the recession - but demand actually increased (health, environment, commuting costs and the bike2work schemes). So they'll be less cheap stock knocking about. Also, there are reports that prices are going up for 2010 and 2009 bikes will stay much the same.
Looking back at older bike specs, it also seems that companies can reduce the spec of a particular range of bike - that way, thy can keep the prices similar. Which means the previous model is a better machine.
As I'm using the cyclescheme.co.uk bike2work plan, I probably won't get sales prices - just RRP. Also, Kona Dews in the past have just changed colour and maybe reduced spec year on year. So I'm happy with getting the one 2009 model i managed to find - you never know - the new 2010 model may be some horrible garish pink!
So if you find a bike you like, go with it.... it's like mobiles and TVs - as soon as you get it, something better comes out