It DOES mean that if you are truly saved, you will never fall away.
So those who "fall away" although they "were once enlightened and ... partakers of the Holy Spirit" were not truly saved?
“So those who “fall away” although they “were once enlightened and ... partakers of the Holy Spirit” were not truly saved? “
In order to be consistent, the answer would have to be “yes.”
Apparently, we can be enlightened, taste the heavenly gift, become partakers of the Holy Spirit, taste the good word of God and the powers of the age to come. . . and fall away.
What do these things mean - being enlightened, tasting the heavenly gift, etc.? I don’t pretend to completely know, but I think perhaps of Esau. He was a son of the covenant, circumcised (sign of inclusion in the covenant people), son of patriarch Isaac, knew all about God, heard His word, knew about the heavenly promises - yet rejected his birthright (his salvation; his place in the kingdom).
Or Judas, who knew the gospel, professed faith, walked with Jesus, actually kissed Him - yet betrayed Christ.
I assume that is the sort of experience the verse you reference is talking about.
If we want to stretch it to Templeton (I don’t know much about him), say, he was raised in the church, baptized, knew the gospel, read his Bible, got ordained - but was lost.
Paul said this almost 2000yrs ago.
2 Thessalonians 2:
1: Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,
2: That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
3: Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
WE are warned about falling away. Especially into the last days many will be deceived and fall away...
Also in Matt 12 43-46 discusses what happens when a demon leaves ...and then returns to an empty house and the man is no better, but worse off.
So yes, ‘saved’ doesn’t mean forever.