It didn't take long for devs to figure out some sad news. Both the enhanced, second generation Kindle Fire and the new Kindle Fire HD have locked bootloaders. This makes custom ROMs unlikely, although not impossible (never underestimate the genius of our devs!). The good news is that this will probably not stop us from being able to root, and in fact, there is supposedly a root method in the works already. Other than that, a fully hacked device is going to be a tough-nut to crack. As always, we will keep you informed if things change.
Source: Kindle-FireForum via AndroidPolice