(meant to include this in the previous comment)
Most of us trads harbor no doubt that the present Pope can still issue proclamations validly ex cathedra. And besides, we like the guy. So I don't think we're sedevacantist. He's still head of The Church and legitimately inherited the throne. May be in error on some things. Haven't all popes?
There is a difference between personal sin and teaching error. Popes have not taught error.