There's also the people who have had their PS4s for a couple years now and are ready to pick up an Xbox to check out the exclusives. For example, I'm an Xbox fan, but if I was in the market for a PS4, I'd pick up the Pro over base model every day of the week. New hardware gets people super excited and there are enough great exclusives on Xbox at this point to justify it.
Also, there are millions of 4K screens out there with an embrarassingly small amount of native 4K content, so if a console is coming out that promises and delivers true 4K gaming, I'll get that box over the competition every single day just to see what my TV can do.