Livestream QnA just happened, watching the replay now and will edit the summary into this post as I see the points. At work, so it will take a while.
1) solo content will be free, released alongside each expansion, and will give packs rather than single cards. (Quantity was not announced)
2) there are special events planned for the lead-up to Mammoth, including Maiev's release and special Brawls.
3) Changes to Spirit Claws and STB are around the end of this month (so in the next week or so), Hall of Fame comes into effect when the next expansion hits.
4) Hall of Fame cards will not randomly spawn in Classic packs.
5) Will possibly be replacing the removed class cards to keep things even.
6) possibly reintroducing Wild adventures and packs, due to increased support for the format.
7) no intent to use PTRs, possibly if nerfs need testing
8) on buffing, it's not entirely out of the question, but highly unlikely
9) big blog post coming this week about arenas, including upcoming changes.