Unfortunately, you may be right, but we have no way of knowing since Samsung doesn't reveal the processing delay times. However, I think you can probably rest assured that the big problem of noticeable lag is coming from the scaling of resolutions and not from native image processing.
As I have stated in this and other threads countless times, go to your local HDTV dealer and TEST the games that you want to play on the HDTV you are interested in buying. Even if you have to make a long trip to do this, it's better than making such an expensive gamble with a blind Internet purchase.
Finally, if you are interested in buying an HDTV with the sole intent of playing a next-gen system (such as 360 or PS3) I would definitely wait until you actually own the console before buying the HDTV. We don't even know if there is going to be a standard resolution for all games on these new consoles yet! It is pretty certain that X-Box 360 will be displaying all games at 720p but that still has yet to be fully confirmed IIRC.