How do you play Morrowind on the PS3? I have seen two people mention it now. I thought Morrowind was for PC and Original Xbox and backwards compatible (sort of) on the 360. I am sure PS3 doesn't have Morrorwind.
I say like others, keep it. You will get $100 if you are lucky. I know I wouldn't pay more than $80 Canadian so that is what $50 or $60 American? So add in your games, you are not going to get a lot. Like someone mentioned, you may have an itch to play some of your PS3 games. PS4 is not backwards compatible. So once you sell your PS3, that is it unless you buy it again. Look on eBay and Kijji to see how much they are going for.
Also what PS4 games are a must for you to have right now? I don't know your situation, so I just say, wait and keep saving and have both. You are only $200 away, so wait the extra few months to save for it. Who knows, maybe some of the games you want will become cheaper when you buy it.
How about getting a used PS4 if you can't wait? Also keep looking for sales. I saw on IGN that there are great deals for Xbox Ones and PS4s if you go the way of Amazon or what not. So keep an eye out for them as well.
So keep what you have. Enjoy what you like right now and keep saving.