You can watch movies on your PS4 and you can stream music, videos, and pictures straight of your PC and/or your media sever. So I don't know what you're talking about. It's also got USB support and you can upgrade your hard drive. It's just not backwards compatible. You CAN however play PS3 from PlayStation now.
Essentially the PS4 can do all that plus more.
yes you can stream but you can´t play videofiles from a USB flashdrive or play music and video from an external HDD. Trust me I tried that recently on a friends PS4. It doesn´t work. There is no option for accessing videos and music from an external drive or USB drive. I am not a fan of streaming or using media server. I often put my files on an external HDD or my USB drive and just hook those up to my PS3. PS4 is more geared towards online services, social media, streaming etc. Playstation Now is another web based service but why using that and paying extra money if I just can play all those games on my PS3 as well? Not to mention that most of my games are digital PS3 versions.
I WILL be getting the PS4 probably next year (when RE 7, Final Fantasy VII, RE 2 remake etc. come around) but even then I won´t be selling my PS3 but will continue to use it for all the stuff I got stored on my external HDD and watching my TV shows (I download new episodes on PC, put them on USB and use that to play it on my PS3)
But anyway just did a bit of research and indeed these videos are all just mods. No new DLC for the Remasters. They look pretty cool though.