The best information available at this particular moment is that the 2006 USDM Civic Si will be available in coupe only.

It will also supposedly have either the K20A2 or K20Z1 motor, and the new Honda Civic Si might replace the entire Acura RSX lineup.

Honda seems to feel that Honda USDM suffered sales losses under the current marketing, and that they'd get more overall sales if they only sold one Civic Si instead of both a Civic and an RSX.

At least, this is what I'm hearing at the moment.