Decent chance that it will be the highest quarter ever, but it won't be by much. Just barely above 12m at best.
If it was such a sure thing, Nintendo would have upped their forecast by more. It wasn't even a month ago that they said 24m for the year and 12m in fiscal Q3 would already eclipse that; Switch is already above 12m in the first two quarters of this fiscal year.
One important reason why these numbers don't add up is that large shipments in preparation for the holiday season went already out in September, so an inflated fiscal Q2 is going to bring down the potential of Q3. Another reason is that Nintendo knew that their lineup for the holiday quarter is light this year and they aren't banking on momentum to remain sky-high for sure. And then there's the fact that only Nintendo knows how high their Switch production really is.
I expect Q3 shipments to fall into the range of 11.00 to 12.25 million.