I am torn between it being this year or next.
I believed it would peak this year as I expected sony to drop prices. Makes sense seeing a $199 PS4 and a $299/$350 PS4pro selling much better than the would at last years/current prices.
But then looking at the games coming out next year, and the possibility of there being a bundle for most of those games on the PS4...... its hard to not see it selling even better or at the very least being flat.
People thought 2017 would be down on the impressive 2016. But you have to remember that while, yes ps4 slim launched and pro launched late 2016, 2017 enjoys those benefits for the entire year and then likely gets the bonus of further cuts this holiday.
Likewise if we see a $199 slim this holiday and a $299/349 Pro, 2018 will actually benefits massively from that too as it's baseline will be higher starting in January.