New sound formats
First gen HD-DVD players, for example, don't fully suport the new sound formats. They will output Dolby HD via 5 channel analog and dolby or DTS lossless via 2 channels. You will also need a way to digitally transmit the new formats (HDMI 1.3) before you can worry about the receiver decoding them.
I would expect to see the new decoding features on receiver in the next couple years after HDMI 1.3 is out and blu-ray and HD-DVD are more readily available. In the mean time, you can use the multichannel analog inputs from your new player to the receiver.