海外のワーグナー関連HPやBBSをチェックしていて、こんなのを見つけた。
噂の震源は英国Grammophone誌らしいのだが。

http://members5.boardhost.com/joewagner/msg/2985.html
> 1955 Bayreuth Ring
> In this months issue of Grammophone, one of the reviewers mentions that he has heard Testamants forthcoming release of
> the 1955 Bayreuth Ring in stereo. So it is apparently not just a rumor though I have yet to see anything official. Hopefully
> the 1955 Hollander in stereo will be reissued as well - though we have all heard the singers in these roles through unofficial
> recordings, it will be very nice to hear them in good stereo sound.

なお、このBBSは　http://www.wagnerdiscography.com/　の画面左にある
メニューの｢Board｣で見ることができる。