One problem with this theory--sales of the next-gen versions were up last year, not down. The decline in overall sales was due to the drastic drop off in last gen sales (which to the best of my knowledge was not plagued by the gameplay issues that were present on the 360/ps3).
2007:
http://vgchartz.com/games/index.php?...r=Last+Updated
2008:
http://vgchartz.com/games/index.php?...r=Last+Updated
For this reason, I'm skeptical about this "make or break" stuff.