Any idea as to why there were no other documentation updates to this regard? No updated white paper. Nothing updated at https://steem.io/ at all to reflect this change. Nothing here on BCT either (until now). And the blog you posted isn't even noted here on the OP or on the website. 
There is a project ongoing by Steemit to update/replace the white paper. They have been working on various fronts to scale up their resources as the coin and platform has become more popular, but there are many different demands. I don't know when there will be an updated white paper.
are there any plans to add Video-Upload on Steem? Hurts in the eyes to see the Youtube logo over there 
Won't videos make it more heavy for the steam network and everyone? Youtube already provides a superb platform to upload your videos to and then share it as you like, it will take a lot of time to develop something as good as youtube's platform on steam.Only text is stored on the blockchain. Any media is stored as links and needs to be hosted elsewhere (usually people host on youtube and link that in a Steem post).
Various people have looked at creating a platform based on the Steem blockchain that would also host video, but the task is somewhat challenging given the high resource requirements and no obvious vehicle for monetizing the viewing (posting can be rewarded by Steem rewards, but viewing is not). It took youtube many years of losses to get to the point where the volume was high enough to generate significant advertising revenue.