I drove a 328 E-46 yesterday at my local dealer's. I advised him that I was waiting on the Coupe but had just wanted to see how the 328 felt in comparison to the 323. I complained of the low (and likely) conservative horsepower figures on the current 323, since even my Integra 1.8 liter makes 170 horsepower. While I was driving he lowered his voice and said: "This is top secret...but since you aren't going to buy this car, I'll tell you. In 2000 the current 323 will get the 2.8 engine and the 328 will move up and get a 3.0 liter." Now, I know we've all heard rumors of an engine upgrading, but I find it hard to believe that BMW would reengineer a 2.5 only to phase it out. In the dealer's mind, the base E-46 engine will soon be the 2.8. This seems unlikely, unless there will be a Compact or something to absorb the 2.5. Anyway, we looked at the pre-specs on the 2000 coupe and the engine choices are no different than what they are today.
Ask around and see what you find out.