I consider myself to be a fairly neutral gamer in terms of Sony/Microsoft/Nintendo/PC, so I'll weigh in.
The reason to own any piece of entertainment equipment is what it can do for you. The PS4 can do many things, but everything it does outside of gaming can be done by dozens upon dozens of other products, so gaming's what to focus on.
The reason to have, say, a Playstation instead of an Xbox, or a PC, is what you can play on it.
If you have a PC, you have access to almost everything out there. And in terms of "exclusives", PC wins. No questions asked. The PC has WAY more games that you can't get on console than the other way around. Anyone who thinks otherwise needs to do their research.
That being said, quality over quantity, yes? Having exclusives only matters if they're exclusives YOU want to play. You want to play The Order: 1886. And Playstation exclusives have a history of not getting ported to anything else ever. So. How much do you want to play it? Does that outweigh the benefit you gain from selling your PS4 right now? Currently, the release date for The Order is set for less than 3 months from now. Is waiting until then, playing it, THEN selling your PS4 an option you'd consider?
If there's nothing you see past The Order that's been confirmed that you want to play, the question I'd be asking myself is this. "What are the odds that something else I'll want to play will be coming along?" If the answer is not good, sell it. If the odds are at least decent, I'd suggest you keep it.
That's my two cents.