Got pretty excited earlier after I woke up reading that a downgrader was already released. Good thing both my 3DSs had low battery and didn't jumped to the hype train.
There are reports of a new sysUpdater+SULib build fixing NATIVE_FIRM downgrading successfully, so it's not impossible to downgrade fully with ARM11 kernel only.
That said I'm still going to advise everyone to not even think about it yet. Not without a hardmod and not without knowing exactly what you're doing.
Wait a few more days.