The old rumours regarding this threadripper launch did include 64-core teasers. The likely thing is that MSI forgot to re-edit the video when they were told that was no longer happening.
I know what was said to the press during AMD's briefing, nothing was said regarding higher core counts. There was only references to scalability when it came to TRX40.
Yes, there are definitely leaks that are intentional, but this one has the hallmarks of a mistake. It looks like AMD delayed their reveal and MSI didn't change everything they needed to.
My thoughts, AMD didn't want to be seen increasing prices too much. They are launching a 32-core with a $1999 price tag, which isn't that much higher than the $1799 cost of its predecessor given the advantages of Ryzen 3rd Gen.
Wait until Q1 2020, AMD can start 2020 strong with higher core counts and increase pricing without as much blowback. People will be used to the 32-core costing $2000 by then. It also gives AMD a strong Computex.