To get homewbrew (kernel mode, like rom loading) you need 2 exploits.
1 user-mode, 1 kernel-mode, finding a user-mode exploit is easy, finding a kernel-mode is difficult.
The user-mode exploit is the entry-point for executing the kernel-mode exploit, you need some way to execute code or nothing will happen.
Currently the only known user-mode exploits are retail-game exploits, like modified save games or for example qr-codes.
The reason why gateway says that people should stay on 4.5 is most likely because they don't have a "free" user-mode exploit and on 5.X - 9.X you need to buy a retail exploitable game (or eshop...) to activate the kernel-mode exploit, just like ssspwn (of course if you stay on 4.5 you don't need the retail game, just a NDS flashcard).
And the reason why they announced it now is likely because ssspwn should be released next week and it is a free user-mode exploit for them as entry point, so why not make a pirate solution from ssspwn, all what they need is a kernel mode exploit (they should have found one now...) and ssspwn.
The fw 9.X has nothing to do with this exploit, it just makes sure that you are on the latest fw to go to the eshop and buy the exploit game as fast as possible before it's removed and to make sure that their fw patcher works.