Spot on mate,
If you don't have any homebrew installed and its from a PAL disc, update as normal.
The Wiikey 2 will not let you run any NSTC updates on a PAL console.
You may loose the region free ability of the WK2 if the update takes the console to 4.2 (this is really unavoidable). The best solution for this is to use geckoOS to launch your NTSC games.
Enjoy your new game
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