In the past the sessions have not been streamed. However, while I was unable to go to InstructureCon last year, a few of the Keynote sessions (ones presented by Instructure employees) were streamed. I was very thankful that I could at least watch those. Also if you are active on twitter and follow the #instcon tag you will get a good feel of what is happening. I was even able to get someone to ask a question for me during a session via twitter and got the answer sent back. This community is awesome and is always will to get/share information.
As for them being posted, I want to say about a month or so. I believe that there are some quality checks that make that take a little time. They do come in a wave over a couple of days. Just looking at the playlist from last year (InstructureCon 2016 - YouTube) a good number of videos were added on August 9th which is just a few weeks later, while a few were added as late as mid-September. Not a bad turn around time IMO.
Hope that helps!
