For purposes of this particular myth (and thread), its point One that is under discussion.
1. In certain types of (rare but real) scenes where 30Mbps is not enough. Higher bitrate (= headroom) is always better anyways, Imo.
2. When mpeg2 becomes a free codec. Studios could then use BD50s and Mpeg2 to encode movies even though they could potentially fit them within 30GB size and 30Mbps bitrate with advanced video codecs.
I say "Never say Never". You may disagree. I prefer to support the format that gives me a fallback in case someday studio compressionists say "Title X (imagine X = your fave movie) really could use higher bitrate in so and so scenes."