3.) Some of the recent games still have major DLC on its way.
When my friend asked me about selling my PS3, I immediately thought about games like The Last of Us, Grand Theft Auto V, and BioShock: Infinite. All three are recent blockbuster titles that still have major DLC on its way. The PS4 ports of these games may take a long time or may never even happen.
If I sell my PS3, then I wouldn't get to play all of these expansions. Funny how my friend who asked me this question forgot that he bought a season pass for one of these games.