My original post was intended to just be a question about the upcoming S8's dual-sim possibility... however this thread ended up being the main S8/S8+ thread, so I'm modifying my original post to include some main points that we've gathered about the device and provide some useful resources:
Misc FYIs
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All MSLs appear to be 000000
To force band 41 only (thanks Terrell352):
##DATA# MSL 000000 then go to LTE and turn off b25 and b26.
##debug# works on this