Your assumption is correct. This was the intent behind these endpoints. We are working on getting new replacement endpoints available.
Before taking action on these three endpoints we looked at which ones were being actively used, in order to make a call about disabling versus depreciation. The live_channels endpoint was actively used, so we have done what we can to provide continuity. The other two endpoints were not critical to the operation of any extension, so to minimise risk, we disabled them.
An update about a new live_channels endpoint should be coming very soon.
I know that this is not the greatest answer, but it is something that we are trying to be transparent about and are actively working on.