Nintendo updates can potentially brick it...but there are so many ways around that, seriously...it's kinda impossible to truly brick a Wiikey modded Wii...What modchip do you have? Make sure you keep up with the firmware. Everytime Nintendo releases an update, Wiikey and the other fully upgradable modchips release one too.
If you end up needing a new Wii, I suggest you go with VeeModz to mod it...you'll have to ship it if you aren't in Toronto, but if you ever need a repair, he can remove a Wiikey install so well Nintendo doesn't know the console was ever modded, lol. That guy is amazing.