I am 85% sure that will be October revile, its hard to predict actual date but I can narrow possibilities:
-Next week is Paper Mario Color Splash week, with reviews, marketing and launch, so definitely will not be any NX infos next week. -10. October new Pokemon presentation, hardly will revile just one day after that.
-26. October Nintendo FY meeting, so need to be before that date.
-Nintendo almost never revile huge hardware or huge news at begining of week (Monday) and at end of week (Friday), so that leaves Thursday, Wednesday and Thursday like possible days for revile.
So that leaves possible dates of revile: 12, 13, 18, 19, 20. and 25. October.
Chose one, personaly I would go with week before Nintendo FY meeting and week after new Pokemon presentation, so that means 18, 19. or 20. October.
Of Course I expecting announcement of NX reveal around week earlier.