It would be something of a coup for Sony though. MS have said DVD would be just fine, and a popular title needing more than 1 DVD would set tongues wagging. Add to that MS's talk that 1080p would never happen, and then adding 1080p to their console, PR campaigns could certainly start spinning this into a 'MS underestimated next-gen and didn't build a platform forward-thinking enough.'
A good game is a good game, and if it spans multiple disks to add the quality gamers want, huzzah. But I think that would be a negative thing for MS, and they'd much rather have a great game that fits onto one disk, 'proving' BRD isn't needed.