This year is the peak year. I agree that generations (including this one) will be more front-loaded than before, but not to the degree you think.
Even for me 2015 is the Peak.
But I expect a seriusly smaller increase for PS4 and XBO and that the sales will dropped like a rock in 2016-2017. (As is happen for 3ds)
SPECIALLY XBOX ONE.
The 3DS is its own thing with its own problems (Competition from mobile etc). I expect the PS4 to sell 20-24m this year, and then 18-22m next year. I don't think they will fall off a cliff that until the PS5 is out. Keep in mind they still have the $300 and $200 price points to come.
As for the Xbox One, yeah I think it will start dropping off quicker in 2016, but follow a similar trend to the PS4.