The way i understand this, under the old covenant, Passover was demonstrated in the passing through the Red sea (Christ's blood). Pentecost was demonstrated in the giving of the law. Tabernacles was fulfilled 40 years after its original appointment in the crossing over into the promise land. But even then, the Israelites did not posess it as they should have.
In the new covenant, Passover is fulfilled in the death, burial and ressurection of Christ. Pentecost is fulfilled in the pouring out of the Spirit. And Tabernacles was fulfilled 40 years after its intended time--in the removal of the old tabernacle (the destrction of Jerusalem). "But now once for all, at the completion of the ages, He has been manifested for putting away of sin through the sacrifice of Himself." But the church has not learned to walk in it. Just as many in Passover do not walk in Pentecost, many in Pentecost have yet to come to Tabernacles.
Heb 4:7 He again marks out a certain day, saying in David, Today (after so long a time, according as He has said), "Today, if you hear His voice, do not harden your hearts." MT-Psalm 95:7, 8
Heb 4:8 For if Joshua gave them rest, then He would not have afterwards spoken about another day.
Heb 4:9 So, then, there remains a sabbath rest to the people of God.
Heb 4:10 For he entering into His rest, he himself also rested from his works, as God had rested from His own. LXX-Psa. 95:11; Gen. 2:2
Heb 4:11 Therefore, let us exert ourselves to enter into that rest,
