I doubt 2018 will be up against 2017, the PS4 is starting to get old and market saturation is slowly starting to set in, too. There's also not much Sony can do anymore with the price; a 50$ price cut is probably incoming this year but this will be probably the lowest the console will sell outside of promos
I do think however that while the PS4 as a whole won't be up, the PS4 Pro sales will be higher than 2017, slowly drawing closer to the base model's sales
did you see what a one week price drop did in november 2017?
The one thing you so casually dismissed is the one thing that the PS4 can do that matters the most.