People keep saying that they don't use discs any more, because they download games on PS4/Xbox One.
Do me a favour, remove your HDD from your console, unscrew it from the enclosure, and look to see what your data is actually stored on.
It's a disc. It's been a disc all along.
Of course you haven't noticed the lack of warmth, even if you downloaded your game, it's still being played off a disc.
You'll only notice the change when you switch over to flash based storage.
You can even look up reports from people who use an SSD in their PS4.