Mitsubishi Chemical has announced that they will be releasing their new 30GB HD DVD-R DL on the Japanese market in late July. Here's part of their press release, translated from Japanese:

Mitsubishi chemical media Ltd. (The headquarters: the Tokyo Minato Ward and president: Otsuka heavy morality) will put two one side layer 30GB HD DVD-R (write-once type) disk for recording on the market in the end of July this year. It answers demand of wanting to want to record and to preserve the length time image like the high-resolution in the background of a real spread of the digital Hi-Vision broadcasting. In this disk, the digital Hi-Vision broadcasting can be recorded for 150 minutes like the high-definition television image quality (transfer rate about 24Mbps time). I will propose the record media in correspondence and a digital Hi-Vision new age enough to high-definition images that exceed two hours.
Mitsubishi has not announced a price. However, the media is expected to run about 4500 Yen (~$39US). If you'd like to read more, the entire press release can be found here.