"One Lord, one Faith, one Baptism" is not mere wishful thinking. When history runs its course the past, present, and future disparation between occupants of heavenly glory will be staggering, each one having a history of exchanging the truth for a lie and thus losing pure science, each one being reclaimed by the Creator who assumed human flesh for the purpose of bringing the crowning glory of His creation back to Himself.
Unity in the church is not a creation of the Pope, nor is it effected by the political machinations of this or that body of doctrine. From a human standpoint you may be right, however. There are many respects in which Southern Baptists and Roman Catholics agree. A good many from both denominations attend public schools, which schools are obligated to remain neutral where matters of faith and science intermingle.
When Christ comes back, whoever's a Christian or ever lived as a Christian will come with him. Guaran-d***-tee ya that nobody in that number will say "I'm a Roman Catholic" "I'm a Baptist" "I'm a Methodist" anymore.
The unity comes from being in Christ, who is the head of the body. Being in Christ is the thing, and is no temple made with human hands, therefore it can never be a man-made structure, not even Solomon's temple.
Unity was never meant to be one massive organization. That is the lesson of the tower of Babel.