Blizzard has stated on more than one occasion that they do not want the final talent in a tree to feel like it props up the entire spec because it is poor design.
However I don't think bladestorm will feel as beneficial in cataclysm as it does now considering Arms is getting a lot of pvp based love including
#1 pummel in battle stance that costs no rage
#2 keeping up to 50 rage when stance dancing
#3 talent to make all attacks cost nothing for 10 seconds out of every 2 minutes
#4 a five second stun on a 45 second cooldown
#5 Aoe stun / distance closer on a 2 minute cooldown
And several other improvements that I am forgetting about