What happened to cause the decline of the quad? I think it was 3 factors coming together:
1) In 2008 Jeff Buttle was the first skater in a decade to win the world title without a quad. Until that point I don't think anybody thought it was possible - in theory, yes, because the CoP allowed it, but not in reality. When skaters with shaky quads or no quads at all saw that they realized that they had a chance, if they tailored their programs right - especially if the quadmasters made a mistake (as was the case in 2008 Worlds).
2) After that the SoV was reworked a little, and the value of the quads and 3A was raised a bit - but so did the penalty. The GoE on a bad quad was enough to render the jump worthless unless you were sure you could land it with positive GoE. The points for a fall on an underrotated quad were ZERO - as if you attempted nothing, while you could score 1.5 points for a nice 2T, so why bother?
3) At the same time, several prominent quadmasters retired/sat out 2009 - Lambiel retired (then came back), Takahashi took a year off for health reasons. That basically left out Joubert and Verner, neither of which had a particulary consistent season. Again - why bother with something risky when you can skate safe and trust the quadmaster to make at least one mistake, which would be enough to win.
But this thread carried itself into Vancouver, where Lysacek, who no one will "accuse" of being the most artistic skater (the "Yagudin" of the match), won without a quad against the old master Plushenko (not quite the "Goeble" of the match), who landed a 4-3 and made no "visible" mistakes - I mean his landings weren't as good, but he did not fall and I think not even a stepout (it's not as if I want to see either program again to check). This caused a lot of peple to say "Huh?" and the ISU to take a step back and reconsider.
Would Plushy have won under the new rules and SoV? Yes, by a narrow margin (about the same as Lysacek's narrow margin). As many people would have been happy with that as with Lysacek's win (maybe they would be from other parts of the world). It was a close competition, anyway.
A more interesting question would be - would Joubert have won against either Takahashi or Chan in Torino, where he landed two quads (neither perfect)? Remember, Joubert landed 2 quads and 5 triples, fell on his 6th triple, while Chan landed 7 triples and fell on his 8th. Which is better? Well, I ran the numbers, and while Joubert would have received a lot more points that he actualy did in Torino, Takahashi and Chan would also have benefitted from the new combo bonus and Dai would receive the new base value for his underrotated 4F, so the order would have remained the same, although the result would be much closer. Are you satisfied with that?
Anna