Messaging: Microsoft will supplement the persistent, private, and group chat capabilities already in Teams with additional capabilities by the end of the second calendar quarter of 2018. These coming features will include screen sharing during chat and federation between companies.
Meetings: Teams already offers screen sharing, meeting chats captured in the channel after the meeting and a preview of audio conferencing. Microsoft plans to add meeting room support with Skype Room Systems and cloud video interoperability, allowing third-party meeting room devices to connect to Team meetings by the end of the second calendar quarter of 2018.
Calling: Teams already has a number of calling capabilities. More are coming by the end of the second calendar quarter of 2018, including the ability to use existing telco voice lines to activate calling services in Office 365.
I asked Microsoft when some of its advanced calling features, like Cloud PBX (known from now on as "Phone System"), PSTN Conferencing (now called "Audio Conferencing"), and PSTN Calling (now dubbed "Calling Plan") would come to Teams, PSTN Conferencing is now in preview and Calling Plan is coming by the end of Q4 2017. These kinds of features are key components of the high-end Office 365 E5 plan.
Update: Here are a few more dates and details from the company worth noting.
On the messaging front, Hide/share/mute chat is slated for Q1 calendar 2018. Skype for Business interop and federation features, such as Federated Chat between Teams and Skype for Business; contact groups; unified presence; importing contacts from Skype for Business and Skype for Business interop with persistent chat are also coming in Q1 2018 (towards the end of the quarter). And Skype for Business messaging policies should be supported in Teams by the end of Q1 2018, too.
On the meetings front, support for broadcast meetings, cloud recordings, Federated Meetings, large (greater than 250 particpant) meetings; lobby for PSTN callers and Outlook meeting scheduling from other platforms like Outlook for Web and mobile are all Q2 calendar 2018 features. Support for PowerPoint load and share and whiteboard and meeting notes are also Q2 2018 features, as is Surface Hub support.
On the calling front, while many enterprise-grade features are coming by the end of Q2 2018, a few like call parking, group call pickup, location-based routing and shared-line appearance are not going to be there until Q4 2018. Call support between Teams and Skype Consumer is a Q2 2018 deliverable. Support for Windows, Mac, Edge, iOS and Android devices and TTY support are due before the end of this year, however.