If you have a backup of any sysnand / emunand yes.
If Nintendo were to patch arm9loaderhax and you update, thus overwriting arm9loaderhax, you could restore a previous nand dump and be right back in business.
If you have arm9loaderhax and BSOD while using godmode9, hardmod will fix it as arm9 won't have access to NAND.
Long story short, hardmod = direct read and write access to NAND. That's why it's stated to always make a backup of either 9.2 sysnand or whatever the latest firm you have installed with arm9loaderhax.
And if 11.0 get's patched via a native firm update, than that is all that could kill it currently.
Ninja'd to add the last line of text.