This quite excellent indeed.
I'm glad you appreciate it, but I want to stress that I am saying something different than you have been saying.
IMO, the Lord will successfully fully sanctify most believers.
Yes, but for all of us, the practical sanctification of our persons will not be complete until the Day of the Lord. Granted, we can make enormous progress, but there will always be work that has to be done. We are children of dust and have not become what we will one day be.
Multitudes of people in the churches think they are true believers,
butski they are involved in habitual sin.
True believers can still be caught up in habits of sin (aka "habitual sin"), simply because many don't know they have a choice, and those that do are still working out their salvation (the practical effects of it) with fear and trembling.
Will they wake up and repent?
If it happens, it will be because they hear a balanced Christian message that does not claim that we have to achieve a certain measurable level of performance for the Lord to consider us one of His children. There is a transformation of focus that begins at true repentance and discipleship. It often doesn't happen immediately when we initially respond to the gospel, but it happens as we press on past the early stages of faith and begin learning from Jesus.
These people are nowhere close to being disciples.
You are not necessarily the best judge of that. Especially when discipleship has not been effectively taught in popular circles.
I agree that most modern presentations of "the gospel" are actually explanations of the atonement with a call for a transaction of our sin debt for "heaven," and not the call of Jesus to "repent for the Kingdom of God is at hand." But at the same time, there is a wideness in God's mercy for those who are not terribly faithful (Luke 12:47) - and even for the ignorant (Luke 12:48). There will be many surprises on the Day of the Lord.