I think you seriously underestimate how much space and bandwidth video-hosting and streaming actually requires.
Just an example - one of my videos that's at 1080p 60FPS that's 14 minutes long has a size of 0,784 GB - and that's a not very long video, though it is very high quality.
I don't know much about server hosting so don't destroy me too much about it xD I'm just talking down the road, anything is possible. If people want Steemit to actually grow how they want it to grow. If we wanna take over social media platforms for content creators we're gunna have to get there eventually.
There are plans for a blockchain based video service - called SteemQ BTW - but I doubt Steemit.com will directly incorporate video hosting itself - it may just implement embedding videos from SteemQ the same way it does for youtube now.
It should be possible with side-chains, using this 'fabric' architecture we have heard so much, (and so little) about. I hope it's possible, because it would be epic!