We’re currently working on defining a compact mode experience. I will post more details when we have more to share.
At minimum, I expect regular updates from Microsoft on this thread on this, given the very high interest from customers. But that's not what we're getting. I've posted here before - but as a large metro hospital, it's imperative that we have a chat client that has a small footprint, and doesn't take up most of the display. Microsoft is forcing their customers to Teams from SfB Online. The common sense approach here would be you, then, give your customers a reasonable/viable alternative to that client. You can't take a hammer away from someone framing a house and tell them they need to use a jackhammer from now on. That usually doesn't end well for either party.
This needs to be done NOW. You can't afford to go down to the wire, Microsoft, on this. We only have 22 months before you pull the plug on us from SfB Online. It takes time and planning for an organization to 1.) deploy a new client, 2.) train their end-users and 3.) migrate users over to Teams from SfB Online. You should know that. Or does it take a number of organizations - like ours - to move their $3.2 million/year (or more) investment in O365 to another solution to wake you up?
Given that Microsoft is now forcing us to move to Teams by end of July 2021, they had better give us an IM client experience with Teams similar to the Skype for Business client. We are a large metro hospital. Most of our Skype for Business Online users are using the SfB client just for instant messages. It's not practical for users to use an application that takes up as much screen real estate as the current Teams client does just for chat. No one works that way. And, we shouldn't have to deal with an endless line of upset/frustrated customers within our organization (which is what we'd have) over a change that Microsoft is forcing us into.
We would be interested in migrating our Skype for Business users to Teams - but we have a lot of people who are primarily heavy IM users who would not like the experience of using such a large client just for chat. A compact Teams client, or compact mode within the Teams client is a "must-have" before we would consider migrating to Teams for chat.