They probably told 4.5 users to stay on 4.5 because future firmware updates from Nintendo may block Gateway, and thus they don't want to be getting complaints from 4.5 users who accidentally updated to 9.3/9.4 trying to get to the "new" supported firmware. I don't think they said that because 9.2 support will have less features. Though it might have less features in the beginning since they are building things off a new exploit, so the old launcher.dat method will likely not be what they use in the new exploit.
But ultimately, the new 9.0-9.2 support should eventually have emuNand support. If 9.3/9.4 does indeed block Gateway's exploit like everyone seems to be expecting, then that's all the more reason to work on getting emunand working. That may be why they haven't released the update yet. They want emuNand working out of the box.
This was my guess, although with 9.3 blocking GW I'm almost hoping they're just faking out Nintendo, saying it's been patched, and then suddenly when the NA N3DS comes out, poof! "Hey guys, we support 9.3 now!". I'm mostly guessing this is the case because they haven't released anything as of yet, and it's already been stated that the ninjhax fix is only a partial fix in the first place (I believe you can still execute ARM11 usermode code, although just not as conveniently as before). So if the ARM11->ARM9 escalation is still there (or whatever they have going on) it might be possible. Maybe. I still have a 9.2 3DS so I'm good for now, but if I get an NA N3DS it would be great for Gateway to work on it, or even better, have the ability to at least downgrade to 9.2 for ninjhax to take advantage of the extra goodies with the N3DS.