The licence used to be a tax on reception of broadcasts. (Streaming live counting as the same.)
Now it also is required for catch up iPlayer, that has broken that logical model.
Ideally we would have a Sky style subscription for the BBC.
However, since this would require a huge re-investment in equipment, this is not feasible just like that.
In the interim (which would realistically have to be at least a decade).
Streaming of non-BBC live TV should not require a licence - (simple to implement)
Any new broadcast tech, (e.g 4K) from the BBC would be encrypted and require activation with a TV licence.
(Any equipment that was only capable of the new system would not need a TV licence to use, except for BBC. Obviously, most kit would still be capable of the current system, so this would be a niche.)
The unencrypted BBC service would be switched off after 20 years maximum and the TV licence would be replaced by subscription. With reviews for 10 years and 15 years,
However whatever happens, streaming non BBC TV live should not require a licence.