In the case of the Switch it all depend on Nintendo stock, doesn't really mean much if September is a better month than August/July. Though recently we saw some new big shipments so... i may change my prediction.
For PS4, August sales are around 191,000 units estimated. Destiny 2 so far is looking like a big drop compared to the first one, and i honestly don't see people buying PS4 for it, Destiny fanbase already has a PS4. Same can be said for FIFA, NBA, and literally everthing in this month. There is a Destiny bundle, which is very expensive tho and he didn't do very well on Amazon, so i don't expect very good performance for that bundle. Imo, PS4 is definitively gonna have a smaller increase MOM compared to last year, while she can still be up YOY, it won't be by a huge margin, after all, last year we saw a price drop and Slim release. I honestly only expect a 15/20% increase in weekly sales, not much more than that.
Same for XB1. Nothing which can have a big impact this month, Destiny, FIFA, NBA ecc all games with a fanbase on XB1 who already have the console, there is no pricedrop or new bundles, so the MOM increase should not be very big. Just look at June for example, even June usually is a big increase over May. yet XB1 only saw boost from 109,000 to 153,000, i think Agust > September should be a similar scenario, or barely better at best.