Thought I'd do a little speculation on what the 2010 bikes might look like and provide a little reasoning.

Touring Bikes - Why would HD spend all that time redesigning the chassis? They needed something for the torque the new water cooled engines are going to produce.
FLH - Remains with the TC air cooled engines at least for 2010
FLT - Gets a new water cooled engine. HD has been testing a couple of engines, including an 1800cc that would make a great addition to a new line of touring bikes based on the FL touring chassis.

Softail
Expect to see these with the TC engine until 2012. Too many traditional riders will want this design to stay were it is. This is also the hardest bike to take to water cooled.

Dyna
The Dyna riders will accept any well designed HD engine. Rumor has it that HD has a smaller displacement version of the 1800cc engine they have been testing that I suspect will go into the FLT. But HD could also pull a fast one and put a big inch version of the V-Rod in the Dyna's. I would love to see a big inch version of the V-Rod engine, but I'd put a 50/50 chance of a 90CID version of the FL engine showing up in the Dyna's.

Sportster
Isn't it about time that Eric Buell provide that nice 1125 engine back to the XL's? I wouldn't hold my breath, but I suspect this is the direction for the XL's. Don't expect the XL's to go water cooled until 2012.

Why do I make these predictions?
I listen to Touring Riders on a daily basis. They want the water cooled bike. So introducing an 1800cc water cooled bike would be good for their sales. It would be good for their stock price and I understand there is some financial incentives from EPA for HD to make the move in the Touring bike line. But if they put out a smaller engine size (maybe a 90CID), FL riders that have been conditioned to assuming that bigger is better might not go to the water cooled engine. So I think HD has to go with the 1800cc engine they have been testing.
The smaller water cooled engine that is rumored to have showed up for testing is either a 'red herring' by Harley or is for the Dyna's. The Dyna has often been a technology demonstrator for H-D in the past. Plus the Dyna riders are generally very willing to accept the new technolgy. Give them a 90CID engine with 80RWHP/90ft.lb. torque and most will be very happy.
The Softail riders are very traditional. The TC engine is most likely here to until the TC engines EPA certification runs out in 2012.
The Sportster riders would love to have the 1125 engine, but the cost increase would kill sales. Expect the air cooled engine for the same reason as the Softails.

We will not have to wait long to see how close I might be. I'm probably way off base, but it is fun to speculate a bit based on the little bits and pieces of info that have shown up.