Absolutely understand where you are coming from. Unfortunately, the only roadmap at the moment is https://www.microsoft.com/en-us/microsoft-365/roadmap and there is nothing on there or nothing I have heard of. Unfortunately, I would agree with Adam here as it being highly unlikely, hence why Skype exists 2019 and everything in 365 is moving to Teams.
It would be very short-sighted of MS to restrict such services to Online only. There are many organizations with significant proprietary data that should never be on a public server. This prevents organizations with Enterprise licenses to fully employ the tools available as part of their purchase.
Working a lot with EU governments/ government agencies - #GDPR and #CloudAct makes #Teams a solution out of scope for all EU based government agencies - a huge market that obviously also will affect #O365 sales/licenses.
All strategies/architectures I have been working on are #Hybrid based.
To me when everything in the stack is virtualised and containerbased services connected w #API it would be strange not to be able to run #Teams on premise either through a virtual implementation of the product itself or through an onpremise #Azurestack.
Anyone from @microsoft that care to comment on this?