IF they aren’t sufficiently culpable for the sin of schism than they are in fact inside the Church, and they are in fact Catholics, but only God knows for sure.
On the contrary, they are sufficiently culpable for the sin of schism to earn an eternity in hell, this is because they have all the time right now while they are in this world to use the brain and the use of reason that God gave them so that they would devote the time and effort to find out the truth. The choice is the same for them as for the rest of us - if they seek the truth, they will find the truth - then they have to live according to the truth the same as the rest of us. We are all the same in this regard. But since they choose to not seek the truth - they *will* suffer the consequences of being wrong.
Schism is a mortal sin, and whoever dies in that sin, it is the same as it is with any other mortal sin(s), they *will* go to hell forever. While they *might* have less culpability then some others, they, like us all, will be judged according to God's word, His teachings and His laws - all of which He left with His Church which is the only place to find truth and live according to it - which is why outside of that Church, there is no salvation. They certainly will not be saved according to their own idea of what they determine or think should be acceptable to God.
"But he that knew not, and did things worthy of stripes, shall be beaten with few stripes. And unto whomsoever much is given, of him much shall be required." Luke 12:48
God says right here that if you don't know, you're still going to get it, He never said that if you don't know, you're innocent. If they aren't sufficiently culpable, then the best course for us all to take, is that of complete and total ignorance. In which case, ignorance truly would be bliss - the more ignorant, the better.