The only advantage I see to integrate a chat or video calls is to contact with specific persons who have accounts in ownCloud in an easy way.
The problem is that, in order to make this work, you require the other person to be active, which means he has to have an active session opened in ownCloud. I won’t count on this because most of the ownCloud’s usage is to upload / download files. I mean, how much time are you active inside ownCloud?
If the approach is like “professional” platforms such as zoom, gotometing or webex, where you open a room and people somehow joins at a determined hour, then what is the advantage of opening ownCloud instead of zoom or gotometing? If it’s just privacy, I’m pretty sure you can find alternatives on-premises which are dedicated and designed for that use case, and will do a better job than ownCloud can.
Note that for every piece of software ownCloud develop, it’s ownCloud the responsible of knowing every nook and cranny about the solution.
You also need to take into account that ownCloud has to push as much as it can for enterprise. If we talk about video calls, I think ownCloud would need to guarantee at least 25-30 participants in the same video call, probably more, without the call being slugish. And we can easily add more pressure by adding 2-3 calls at the same time.
Even if spreed (or whatever platform) takes care of this, ownCloud would need to know how things can be deployed in order to provide good support to its clients.
As said, I don’t see any breaking advantage that would make big enterprises to switch to “ownCloud calls” instead of using whatever they’re already using.