Neither is the most elegant solution, and it doesn't take into account whether you already own any of the games. That means you'll have to pay again for your PS3/PS2 nostalgia.
As for the PS4, there's two ways it's dealing with backwards compatibility. For PS3 games, there's PlayStation Now. This cloud-based streaming service allows you to play PS3 games on your PS4 by streaming them over the internet, with payment taken on a rental or monthly subscription basis.
You can still pick up the latest PS3 Super Slim brand new for £165 for the smaller 12GB model, or around £200 for the larger 500GB version, which you’ll want for storing all your games.
They have announced recently that the ps4 will have dlna streaming fairly soon. Due to public backlash. Plus mp3 support. Personally I will wait for this before buying as I still use my launch day ps3 as a media streamer for my mp3s(legally bought) and to watch my home videos. I was going to buy on launch day but as its a reduction in functionality I will wait. But worth clarifying that it will come. Ps3 didn't have on day one, but considering most new tellys and blue ray players support this its difficult to see what they would achieve by leaving this out. Its just waiting for a firmware patch. In the mean time it means when I do get it I can buy some pretty owned games.Another difference is you will need PlayStation plus membership for online gaming. Annoying but still cheaper than the Xbox equivalent and Microsoft have proved this works as a business model