We haven't yet seen any official confirmation of the news, but it's been reported that the 51GB triple-layer single-sided HD DVD Toshiba first announced at CES has been approved by the DVD Forum. (The last we heard about this, the new format had been submitted for approval.) Of course, this might mean consumers will need new players to read 51GB HD DVDs, which could potentially damage the format more than help it; the last thing either HD DVD or Blu-ray need right now is to fork hardware compatibility with their own embattled formats, so we'll hope what we've heard about 2nd and 3rd gen HD DVD players being able to read 51GB discs via firmware upgrade is true. Also up to bat: the "twin" dual-layer DVD / HD DVD combo-disc was also approved, with one 5GB DVD layer and two 17GB HD DVD layers. We'll let you know when the DVD forum officially confirms (or denies) the news.
Read - News of the new approvals
Read- AVS Forum thread