Thank you for sharing your plans. I am afraid that I have a negative response. I will do my best to share the source of my reaction.
I am involved in Stack Overflow and Stack Exchange because I believe in the original mission. Our mission, as I have always understood it, is to build a high-quality archive of knowledge that will be useful to others in the future, in the form of questions and answers. Not a social site, not a discussion forum, not a place to build community, not a place to interact with other knowledgeable individuals, not a help desk, but a shared effort to build a knowledge base that is useful for humanity. Optimize for pearls, not sand. A combination of the best of Wikipedia, Reddit, and blogs. That is the basis on which I have participated in this site. That is always how I have understood the purpose of Stack Overflow. It's a mission that the founders articulated with great effectiveness, built a group of users around, and designed the site to support.
Now the company comes presenting a vision which does not seem to advance that mission. Indeed, I interpret the post as saying that the company is focused on things other than the original mission. I interpret this as saying that the mission, as I understood it, is not so important to the company; the company's priorities are elsewhere, in expanding in directions that are orthogonal to that mission.
I find this disconcerting and disappointing. What happened to the mission?
I see Stack Overflow as a place that is polarizing -- in the best possible way. Some people love it and are deeply energized by the mission and become power users. Some people hate it (and they go complain on Twitter). To me, this sounds like a great thing, it is what has powered Stack Overflow and enabled it to be so successful. It doesn't need to appeal to everyone -- it just needs to find a core group of people who are inspired by the mission and pour their time into its success.
I find it sad that this seems to be lost. The company seems to have lost its way and lost its connection the mission. Instead, the company seems to want to be something for everyone, and the old mission doesn't seem to be prioritized any longer. The company views it as a problem that not all users love Stack Overflow, and is trying to find something for those who are left out (e.g., who don't feel a particular connection to the mission). And as I look at what is being proposed -- Discussions -- I see something that won't contribute to a high-quality knowledge base and I suspect will suffer from all the problems of discussion forums that originally inspired the creation of Stack Overflow. (The world doesn't need another php discussion forum or Experts Exchange or Yahoo Answers or Quora.) There seems to be little point in offering feedback on the details of the proposal, as the values and mission seem to be off-base.
So I view this with sadness. New people have arrived at Stack Overflow and are in charge, and the original mission doesn't seem to be the priority any longer. The company has other priorities and values. Improvements to the site that would benefit the original mission seem to be a lower priority. From the outside it appears the company is chasing engagement and number of users and such metrics, and trying to be something for everyone. I anticipate that focus will not be healthy for the future of the site. I anticipate that chasing dollars and profit will ultimately be harmful for the site's health and the company's finances.
The future looks negative to me. I predict those users who were deeply engaged by the original mission to continue slipping away and becoming less active as they repeatedly observe the company de-prioritizing the original mission. I predict the new discussion venues will be full of chat and noise, the experts won't want to engage there, so people won't get expert answers to their questions, and when there are useful insights, they'll be buried deep in discussions and so not findable or useful to others in the future. I predict a downslide into mediocrity.
I know staff have shared that they don't appreciate coming to meta and being hit by an onslaught of criticism. I apologize if I'm making your life worse with my negativity. I'm hoping that you will find value in the perspective from one user.