I don't think they will throttle the tiered plans either because they want the $10/gb overage charge.
As for the Att "unlimited data" softcap it will be 2gb before throttling
GUARANTEED...
Verizon just did the same to their users (making unlimited data worthless). That's also a reason why T-mobile started throttling after 2gb since they are going to be bought by Att and want their customers to be in compliance when the transfer occurs.
If anything its better to be on a tiered data plan because if you need more data at least you could pay for more data at fast speeds after 2gb. With "unlimited" your slowed to a crawl after 2gb and are completely stuck for the rest of the month