If you want a huge deal, wait until the end of year deals.
There will be some M3's still on some lots and dealers will be giving great deals.
This also goes for the 135i. The highly optioned 135i's will still be on the lot at the end of the year. Should expect large discounts.
But nothing like the $14-15k off msrp for the 07 M coupes. They are practically trying to give those away.
This basically goes for any car, any brand.