the price they will go down to depends on a few things
1st. what kind of dealer are they msrp or a markup dealer? An msrp dealer will find it harder to part with more money because there really not making that much on the sale to start with. but a markup dealer has more wiggle room to make the sale they may not want to but they can.
2nd.How well are they selling? If the bike is flying out the door at your dealer they will be less willing to part with the money that they may get from the next guy.
3rd. What time of year is it? In July the 2010 model year is supposed to be released that will make the demand for the 09's drop especially if there is any big changes.
So armed with this info you should be able to go into a dealer with a little more swagger and if you do your research on the dealer you should be able to beat them into submission.
good luck