I'm not sure how that's going to work though? Wouldn't game load times only improve after you've been playing the game for a while? The content still has to be copied from the HDD to the SSD after all. If they had a 256gb ssd I guess that would be enough room to hold the most often accessed data from ~2tb of installed games, otherwise if it was small only the most recently installed/played games could be partially cached on the ssd.

Depends on the size of the cache. I don't expect anything bigger than 128GB. It'll be non-volatile, so it will retain enough frequently used data for at least one game. After that it's just a question of algorithm which data to keep in there. I could think they will already copy data into the cache when you're installing the game. So you will instantly have the benefits of the faster load times. The SSD they're gonna use will also be faster than a regular mainstream SSD, so they'll get the best of both worlds.

It's a good solution that will work fine unless you're constantly switching between 5 huge games every 5 minutes, but nobody does that. It's a great solution for consoles because all of its processes are easily predictable and repetitive. It wouldn't work as well on PC where you have much more complex data streams.

This will probably be as much of a solution as mandatory installs to an HDD were on the PS4 and XB1, so it's first and foremost a measure to prevent loading times from getting much longer.