Who will enter the millennial Kingdom?
Only believers will enter the millennial Kingdom. Specifically, Gentiles who believe during the Tribulation through the preaching of the 144,000, along with the remnant of Israel who are saved, will enter. The Kingdom begins with believers only, as it is a time of testing following the Tribulation.
Les explains that the millennial Kingdom is the thousand-year reign of Christ, which is an introduction into the Eternal. He notes that the thousand-year length does not contradict Old Testament references to the Kingdom as forever, because the millennial reign will end and Eternity will continue on much the same basis. As people come into the Kingdom, Les emphasizes that it is only believers: the Gentiles who believed during the Tribulation under the 144,000's preaching, and the remnant of Israel will be saved. This thousand-year reign will be another time of testing.