As far as I know, Lefebvre was not received back into the Church before he died. Therefore, he died outside the Church. But only God knows what the state of this man's soul was at the time of his death. Therefore, only God knows whether or not Lefebvre's soul is in hell.
Dying "inside the Church" is no guarantee of salvation just as dying outside of it doesn't mean that the individual is necessarily damned.
I agree. Of course not. In fact, to whom more is given, more will be expected.
...just as dying outside of it doesn't mean that the individual is necessarily damned.
This statement, however, conflicts with Catholic dogma, as the Church has infallibly taught that outside the Church there is no salvation.
Back to Lefebvre, though. There is also the matter of the possibility of an unjust excommunication, as they have happened before, and to canonized saints. There is the possibility of an invalid or wrongful excommunication, which never truly took place in reality or in the eyes of God let's say.
Furthermore, in the matter of Lefebvre there is the very real distinction that his was not a formal excommunication, but rather, a supposed state of pre-existing self-excommunication, latae sententiae. If he was indeed outside there Church when he died, there was no chance for him unless he had access to reunion with the Church before death, or if he wasn't really in a bad way to begin with. Both situations are quite possible.
We don't know that Lefebvre is in Hell any more than we know that John Paul II is in Heaven.