Also, currently I believe only gstreamer can use the DSP. So mplayer or VLC or whatever non-gstreamer thing will have to do the decoding on the Cortex. Not only am I not aware of any DSP support plans for non-gstreamer apps, but I am not sure if the DSP arbitration allows for third party application.
Nokia have provided the TI DSP codecs for decoding. These will not do 720p like the HD pack but an enterprising dev or company could create better optimised codecs and sell them on ovi store or provide them in extras.