If by "people" you mean humans in the flesh, there are no human beings in heaven. Human beings have earthly bodies designed by God to live on Earth. Heaven is the home for spirit beings. Faithful Christians will receive a spirit resurrection and they, as spirit beings, will live in heaven. 1 John 3:2 (NKJV), “Beloved,…it has not yet been revealed what we shall be, but we know that when He is revealed, we shall be like Him, for we shall see Him as He is.”

To further answer your question, the Bible does not tell us how many people have or will die as Christians and then receive a spirit resurrection. We certainly do not know the number in heaven now. We do know the 144,000 saints will be in heaven, but so will be a great multitude who were less faithful in obeying God. Revelation 7:9, 14 (NKJV), 9 "After these things I looked, and behold, a great multitude which no one could number, of all nations, tribes, peoples, and tongues, standing before the throne and before the Lamb, clothed with white robes, with palm branches in their hands, … 14…'These are the ones who come out of the great tribulation, and washed their robes and made them white in the blood of the Lamb." These dear ones learn to value and to love God above all else when they experience trials. The trials help them to wash their robes.

The only people who will be resurrected as spirit beings are those who have received spirit-begettal to a new life. God begets Christians with the Holy Spirit when they have accepted Jesus as their Savior, and have consecrated their lives to do God’s will. 

Some believe that faithful people in the Old Testament have been taken to heaven. However, these holy people lived before Jesus’s sacrifice was made. The heavenly calling was not yet opened. When Jesus was resurrected, He “…abolished death and brought life and immortality to light through the gospel,” 2 Timothy 1:10 (NKJV). 

Jesus, Himself, said, “No one has ascended into heaven except he who descended from heaven, the Son of Man.” John 3:13 (ESV) The Apostle Peter also stated that the faithful of old are still dead. “Men and brethren, let me speak freely to you of the patriarch David, that he is both dead and buried, and his tomb is with us to this day.” Acts 2:29 (NKJV)

Most of mankind will receive an earthly resurrection. All that Adam lost when he sinned will be restored to the willing and obedient of mankind during Christ’s reign on earth. Acts 3:20-21 NKJV, 20 "and that He may send Jesus Christ, who was preached to you before, 21 whom heaven must receive until the times of restoration of all things, which God has spoken by the mouth of all His holy prophets since the world began.”