How would that work? Who would call it? Who would set the agenda? Who would attend? Since we have never required unanimous voting, what constitutes a majority? What would constitute a quorum? All of these issues exist and prevent any effective ecumenical council from being called now irregardless of papal authority. I'll just throw out a couple of hypothetical examples. Say the Byzantine Emperor was to call a council... oops that won't work. OK, say the Ecumenical Patriarch was to call a council... but members from Russia would not come and 2/3rd of Orthodoxy would not be represented and would not follow anything decided. OK, say the Pope was to call a council... well probably only one side of Orthodoxy would show up, either the Greek or the Russian; but not both. So there is noone in this world that could get together a truly ecumenical council.
Now for hypothetical number two, if we did this using a form of democratic representation, then for X number of church members, a voting representative is sent. Let's use the equation of 5 million members gets you 1 representative. So there would be roughly 240 representatives from the Catholic church and 52 Orthodox representatives. How do you think the Orthodox would take any decisions coming from that ecumenical council?
You see, there is no motivation for the Orthodox church to have such a council and short of an act of God, I don't ever see it occurring. So really, papal authority is limited now to the Catholic Church and will probably never be an issue for the Orthodox, short of a bullet point on a list that keeps such ecumenical councils from happening.