I thought about this same topic quite a bit since a few events back, and more-so since last night's.
I really don't think aggression is going to become extinct. I think fighters that have the natural aggression and can fight the game which ever way it goes(a brawl or a cautious fight) without being taken out of their element are going to thrive.
The problem is that some fighters DEPEND on their adversary to be aggressive in order for there to be a fight at all.
Take Liddell, for his style to be at its most effective, he absolutely needs the other fighter to bring the fight to him, either by trying to take him down or by trying to strike with him. Liddell is taken out of his element if the other fighter is just going stay back and be cautious.
Then there's Machida. For a fight to happen at all, his opponent is going to have to come after him. If 2 Machida's fought each other nothing would happen for 15 minutes.
The problem here is that in order for fighters to be asked back to events and to make big money, they have to have exciting fights, and if you're always depending on the other fighter's style to make it possible, then you're at their mercy. It doesn't mater if you've been beating fools this way for 10 years and they've all been willing to come at you and play your game at the possible expense of losing. You know why? Because it was up to THEM, and not YOU.
The sport may be slowly changing to one of gameplans/strategy, but a naturally aggressive fighter can handle a slower fight, as well as the brawl that ensues when the crowd starts to boo.
HW: Brock Lesnar
LHW: Ryan Bader
MW: Wanderlei Silva*
LW: Clay Guida
FW: Josh Grispi
BW: Brian Bowles
"Let's beat our chests and celebrate with much joy, because this victory is ours!"