Updated with weeks 27, 28 and Nintendo's official figures.
The gap grew a bit these past 2 weeks in favor o BotW, but they tied last week. The gap should grow again next week when Botw is expected to do a bit better.
According to Nintendo tho... BotW (Switch) already surpassed Twilight Princess' (Wii) first full year in under 7 months.
BotW Switch: 4.7m
BotW Switch: 1m (as of March 2017, so it's certainly higher than this)
So, according to Nintendo, BotW is already around 6m. Let's remember it's still to experience its first holiday and is far from turning 1 year old. The road to March 03 shall be extremely interesting!
Bet with Teeqoz for 2 weeks of avatar and sig control that Super Mario Odyssey would ship more than 7m on its first 2 months. The game shipped 9.07m, so I won