The main thing that stands out to me is that first year for the PS1. Hard to believe it started so poorly and still went on to sell over 100 million.
PS1 launched in Japan 10months before it did in other regions, PS2 launched in Japan 7-8months before it did in other regions - that's why both of these consoles start out pretty flat in this graph.
Well, sales got more frontloaded in recent years, so the only really surprising is PS4, as this started off pretty well. And looking at the graph we see, that it can be in part attributed to the different launch dates. PS4 will have it's holiday peak later. Still, if momentum of Switch is good going into the new year, there might be a chance Switch stays ahead.
Other than that we could expect based on earlier Nintendo consoles, that Switch might stop selling earlier than the competition. Although, for Wii it really was the fault of Nintendo who stopped supporting the Wii. So maybe this time it is different. But Nintendo is Nintendo, they could easily do it again.
The Switch would need to ship ~6m next quarter to stay ahead of PS4..