Dino Caputo Thanks for the response!
I think I would have been surprised if Microsoft did have this on their roadmap. My scenario is pretty speculative and early on: My company has Office 365 E3. We are looking at a new phone system, and are pursuing a unified communications strategy. Microsoft's Phone System (either as an E3 add-on, or upgrading to an E5 plan) is one of several options that we are going to be looking at in 2018, along with a solution from Cisco.
In terms of a workplace chat/unified communications platform, we like what we're seeing from Teams so far. It's much better for our needs than Cisco Spark. We are concerned that if we prefer Teams, we can ONLY get Microsoft Phone System and have our unified communications goal solved for. This may be cost prohibitive if the cost of an E3 add-on or E5 licenses is non-negotiable and Cisco/another vendor offers my leadership a better deal on a phone system.
Ideally, I would be able to inform my leadership that Teams will be inter-operable with a range of phone system vendors in the future, but I understand there may be reasons for that not happening or not being announced!