if you have psn+ and dont need the money from selling the ps3 maybe you should keep it for the extra games you are entitled every month. I know ps plus is not as good as it used to be but still if you have psn+ it 2 games per month. Plus you never know when they will enable the external drive, dlna etc support for the PS4 and ps3 supports those.
That is pretty much what I have been doing, using it for the PlayStation Plus games, GTA V and playing 3D blu rays

I'll keep it plugged in, just not next to the PlayStation 4, move it to another room
