Asus has worked on the bootloader. A well known dev (Bumblebee) had posted on twitter a message congratulating Asus for taking the first steps in implementing the code necessary to unlock the bootloader. That code appears in the .13 firmware update.
Bumblebee is one of the devs that found rooting exploits for the TF and TFP so I trust what he says. He is often found in the #asus-transformer IRC channel.