Long story short, someone like Gateway only has to do a hardware mod to a n3DS and thus they will always win the cat and mouse game of updating when keys are changed. They can just allow their modified n3DS to update to latest firmware and use the bootrom flaw to dump the new keys. (Assuming it's also NAND modded, they can flash back to a exploitable firmware when done if it's also their test unit) That's from what I understand. For the rest of us, this flaw isn't of much use because it requires hardware modification to execute.
I suppose some kind of mod chip could get released from this for people who want to dump their console unique key. But I can't immediately think of any use that would have.
EDIT:
Well one use is for those stuck on newer firmwares. One could exploit this flaw to get access to console unique keys, then take a decrypted image of older firmware and encrypt it to the console using that key.
Downgrade via special modchip anyone? I can see a market for that.
This pretty much means the entire 3DS ecosystem as it is now is flawed and can't be fixed. Even if Nintendo releases a hardware revision that fixes the bootrom flaw, there will always be a lot of exploitable consoles and once Gateway gets their hands on this, it's game over. The n3DS just came out, so it's out of the question that Nintendo could release another significant hardware revision that would use an encryption scheme not compatible with the last generation (like a n3DSi or something else crazy like that).