It looks like some people in the thread below have figured it out — we actually have this. You can start a chat both ways; the system will automatically recognize if this person is on Skype for Business or on Teams.
Thanks and let me know if you have any questions.
An error occurred while saving the commentArritx commented
Me too. What's the problem? After a few days it has disappeared.
This feature is still in the works. No additional details are available at this time.
This feature request is working its way through the backlog queue. No new details are available yet.
This item is still in the queue. I’m still awaiting more feedback and hope to have more details to share soon.
Thanks for the feedback.
We are considering a number of ways to better integrate experiences across Teams, Outlook, and other apps. However, we don’t have any specifics to share on this request.