Presumably CCP doesn’t believe it would be worth the development effort to complete the feature and add it to the game - or higher priorities have left it languishing in the backlog.
CSM are our advocates for stuff like this. If enough people want it CCP will reconsider their priorities.
Or, more likely, the senior game designers recognized the downsides of such a feature on open-world PvP and the problematic nature of putting such a feature in a game like Eve and just shot it dead.
We will never see arenas. I would take even odds that the Alliance Tournament doesn’t last another three years. It just doesn’t have enough interest to justify the amount of developer effort and is only living on the fumes of the discretionary time of some devs who still want it to happen. All it will take is a few of them leaving, voluntarily or not, at the same time and that will be that.