Keep in mind its in AT&T's interest to keep your throttling limit as low as they can get away with since it makes you more likely to leave your unlimited plan someday and pay for overages.
I think the only chance that AT&T would raise the limit is if their currently available tiered data plans drop in price to the point where you could get 10GB of data for the same price as what we are paying for unlimited plans throtteld at 5GB. I think that's a ways off yet even with competition heating up with T-mobile.
However, they structured the new plans so that its not exactly comparable to the old ones.